Japanese External Reverse Porro Prism Binoculars.  VIRTUAL MUSEUM

This website is devoted to “miniature binoculars”: small reverse poro prism binoculars with form fitting external prism covers, occasionally called “M Type” (Mikron Type), or skeleton binoculars due to their minimalist appearance, or “vest pocket” binoculars. While first developed in Germany in 1919, these binoculars were produced in limited numbers between the wars and then widely distributed under a great may brand names in the post WWII US occupation of Japan. Most of the Japanese contact manufacturers and trading co/ exporters involved were small and went out of business many decades ago. Information about them has been scarce. As part of actively collecting these binoculars, I have conducted thousands of hours of original research, and have amassed substantial information on what brands were produced, and in what powers, and by which manufacturers. I am happy to share my information as a work in progress. In my hands on experience with over 850 of these binoculars, the great majority of these binoculars have seized oculars due to age hardened optical grease, or have prism collimation or other issues. So after repairing six or seven hundred, I am providing instructions and tips on repairing miniature binoculars of this type to help mechanically inclined optical enthusiasts repair or improve their miniature binoculars. There is a general misunderstanding of Japanese binoculars. The reality is that a group of assembling contract manufacturers produced binoculars using parts they made or bought from sub manufacturers, acting under contracts to exporters, trading companies, and to foreign importers, distributors and retailers. With only a very few exception, all of the binoculars brand names you are familiar are merely distributor marketing names. This applies to binoculars branded as Bushnell, Swift, Jason, Tasco, Selsi, Kalimar, Sears, Tower, Milo, Sans & Streiffe, Focal, Frank Nipole, LL Bean, Boots, Imperial, Brookstone, Compass, Empire, Scope, Yashica, and virtually all other brands of Japanese binoculars you have or have not heard of. Almost every brand was made by a number of different manufacturers ,and almost every manufacturer made batch lots of many brands. There are only a few exceptions where manufacturing companies also directly controlled aspects of their own product marketing, manufacturing and distribution at certain times (Nikon, Asahi/Pentax, RKK), with distribution through licensed subsidiary or affiliated importers and distributors. For miniature binoculars I have identified over 32 actual primary assembling manufacturers, though many other companies made small parts. Even specific models of specific brands were sometimes made by many multiple manufacturers at different times. To give an exampleminiature binoculars made by the prolific manufacturer Seiwa Kogaku Ltd./ Seiwa Kōgaku Kōgyō Kabushiki-geisha / 清和光学株式会社 ( mfgr. code JB93 ) were sold as these brands. Updated 11/20/2018.

 MFGR. JE CODE ON FRAME (common), (JE50 metal parts manufactured by Tanaka Koki Seisakujo. Inc.

MFGR. CODE “NOT HIDDEN” ON EXTERIOR PORTION OF PRISM COVER (less common placement of marking)

J-B7/manufacturer Nikon Corp


  (less common placement of marking)

J-B231/manufacturer Tochihara Optical Co


JB74 assembling manufacturer Omori Sogo Kogaku Kogyo, J-E51/ metal parts Yoshimoto Kogaku Co.

Manufacturer Codes on Japanese Binoculars . Hersteller-Codes auf Japanischen Ferngläsern. Codes Fabricant sur Jumelles Japonaises. 日本 の双眼鏡メーカーコード. коды производителей на бинокль из Японии. Tillverkarkoder på Japanes Kikare. Códigos de Fabricante en Prismáticos de Japón. Codici del Costruttore sui Binocoli Giapponesi.

Logos of Japanese Binocular Manufacturers. Logos der Japanischen Ferngläser Hersteller. Logos de Jumelles Japonais Manufacturiers. Логотипы японских биноклей. 日本 の双眼鏡メーカーのロゴ. Logos av Japanska Kikare Tillverkare. Logos van Japanse Verrekijkers Fabrikanten. Logos de Prismáticos Japoneses. Loghi dei Costruttori di Binocoli Giapponesi.

 MFGR. CODE “NOT HIDDEN” ON EXTERIOR PORTION OF PRISM COVER  (less common placement of marking). J-B69/manufacturer,

Akebono Kogaku Kogyo Co



THE “J-B” above or “JB” mark is actually combined letter JL plus B, as represented above, meaning “Light Machinery of Japan”.


There is sometimes a way to know the actual manufacturer, through stamped manufacturer’s codes, as explained below and shown in the pictures

K ” logo trademark of Omori Sogo Kogaku Kogyo

Prior to and after the JB and JE codes were commonly in use, one can sometimes determine the manufacturer of one of these binoculars by a stamped logo that contains no wording. In some cases it is easy to know what company these logos indicate. For example the “ K ” logo of Omori Sogo Kogaku Kogyo shown above is very frequently seen. One does see other logos that are not commonly known or referenced. See the following for some additional reference materials: http://home. europa .com/~telscope/binotele.htm. Look part way down the page under “trademarks of Optical manufacturers” for documentation of some of the logos established in some of the years 1957-1973.

See the page “ IDENTIFY THIS for more manufacturer logos.

According to Peter Abrams in Outline of Japanese Binocular Production From Nov 1959 and for roughly 30 years disclosure of manufacturer was mandated or encouraged on optical products, including binoculars, as part of a quality approvals scheme (those oval “passed” stickers) by the Japan Binoculars Export Promotion Association But my experience examining 800+ miniature Japanese binoculars suggests the marking practice on them tapered off in the 1970’s. The marking consisted of a combined letter LJ (for light machinery of Japan) which in reality looks like J- plus letter B or E, plus a number.  A “J-B” code stamping is for the manufacturer of  the assembled binocular, and a “J-E” code stamping is for the manufacturer of the metal frame, if different from the assembling manufacturer. Binocular collectors usually refer to these as “JB” and “JE” codes. Around 1955 the Japan Export Binocular Industry Assn imposed production limits (allocations or quotas) as well as price and quality controls on Japanese binocular manufacturers, because production normally exceeded demand. According to Abrams in Aug 1960 the Japan binocular Export Projects Association was created to purchase and export binoculars, but it collapsed in Mar. 1961 with a huge overstock of binoculars, and many of the 203 Japanese binocular manufacturers in operation in 1959 went out of business by around 1961. General documentation of who made what binocular brand 40 and 50 years before the internet has been quite scarce, and to the degree that it exists at all, it may not exist on the internet in English. Some important reference materials have been translated and documented by generous souls like Bill Beacom and Fred Schwartzman, and hosted by Peter Abrahams, such as the 1959 manufacturer’s list and JB codes and historical information at the following:




Confusing Names of Japanese Companies Selling Binoculars Verwirrung Namen von Japanischen Firmrn, die Ferngläser Verkaufen. Confondre les Noms des Enterprises Japonaises. Qui Vendent des Jumelles. Смутные имена Вариации японских биноклей компаний. わかりにくい名前日本の双眼鏡のバリエーション企業. Förvirrande Namn på  Japanska Företag som Säljer Kikare. Nombres Confusos de las Empresas Japoneses  qui Vendieron Prism á ticos. Confuso Nomi di Aziende Giapponesi che hanno Venduto il Bonocolo.

One of the difficulties in discussing and researching Japanese optical (Kōgaku) companies (manufacturers, trading co’s, exporters, purchasing agents, distributors) is that there are multiple variations of each company name: the name using a combination of Chinese derived Japanese characters (kanji) and Japanese characters (kana); the same name using the western alphabet (rōmaji); and then the same name in one or more  “translated” forms where words are presented in some English equivalent. Additionally there are company name changes over time. Using Riken as an example, in kanji it is 理研光学工業㈱ . In rōmaji and partially abbreviated it is Riken Kōgaku Kōgyō K.K, or unabbreviated is Riken Kōgaku Kōgyō Kabushiki-kaisha (or-Kabushiki-gaisha). In “translated” form it may be Riken Optical Industries Co., Ltd. And then like many other Japanese optical companies, Riken renamed itself and became Ricoh, which in kanji is 株式会社 リコー , and in rōmaji is Kabushiki-kaisha Rikō or Kabushiki-geisha Rikō and in “translated” form may be Ricoh Optical Industries Co., Ltd, or several other variations. Additionally manufacturers often had an  associated controlled “trading “ entity with another name. For example the manufacturing entity Toyo Jitsugi Kōgyō Kabushiki-Kaisha also had the associated Trading entity Oriental Trading Co. “ TJK ” for T oyo J itsugo K K appears on binoculars, but so does “ OTC ” for O riental T rading C o. Oriental Trading Co in acting as a purchasing agent/trading co. might handle binoculars other than from its own manufacturing entity, and Toyo Jitsugo as a manufacturer might sell binoculars through other entities than its own trading co. And while ownership would be largely the same there might be a few different stockholders. Back to Riken: In discussing Riken any one of nine or more variations of their name might be correct to use in discussing a pair of binoculars that the company produced or handled, or any one might appear in reference materials you are searching. In addition, an alphabetic company logo or abbreviated acronym might have been used based on any of these variations. In the case of Riken, they used RKK and R.K.K. based on the rōmaji abbreviation of Riken Kōgaku Kōgyō d uring the time that they made these small binoculars. (In general I try to cite the rōmaji names used at the time the binoculars was made).

   One commonly finds Kōgyō K.K. as a part of the name of these Japanese optical company names. This stands for Kōgyō Kabushiki-Kaisha, (which may also be equally correctly spelled Kabushiki-gaisha), with Kōgyō roughly translated as “industries” and K.K. representing either Kabushiki Kaisha or Kabushiki-gaisha, which may be translated as “industries” and “company, Ltd .”, but may also be translated as “corporation” or “incorporated” or “joint stock co” , but without really being exactly the same business structure as would be for a company using those terms as legally defined ones in the USA. Sometimes Seisakujo is substituted for Kabushika-geisha, and Seisakujo roughly means “factory”, which, as in English, is more of an informal description than any specific legal business structure. It is therefore possible to interpret two Japanese co. name variations as being separate entities when they are not, but is also just as easy to interpret identical or nearly identical entities as being the same when they are unrelated. For example there was a Seiwa Kogaku Co. Ltd (which translates as Seiwa Optical Co Ltd.) that was completely unrelated to another entity called Seiwa Optical, Ltd. And there was an Asahi Kogaku K.K. that made cameras and binoculars (and became very well established and eventually morphed into Pentax) and there also was a completely unrelated entity also named Asahi Kogaku K.K. that made cameras and faded into obscurity, and a third company involved in binoculars names Asahi Kogakuki Co Ltd completely unrelated to the other two. Likewise there were at least four unrelated Japanese binocular manufacturers whose Romanji names spelled out K.O.C. and who were known to have used K.O.C. on markings on binoculars . So what K.O.C. signifies depends entirely on contextual subtlety. The company associated with miniature binoculars using “ KOC ”, K uroki O ptical C o. is known to have additionally used ‘ KOIC ” for K uroki O ptical I nstrument C o at a slightly different point in the company history.



Miniature Binoculars Model Number. Miniatur-Fernglas Modellnummer. Numéro de Type des Jumelles Miniatures. Номер модели. Miniatyr Kikare Modellnummer. Miniatura Prism á ticos Números de Modelo.

A few of these small binoculars display model numbers on the prism covers. Since almost all have serial numbers, the serial numbers are often confused with being model numbers. The Swift brand in particular frequently displays model numbers, as does Tasco.  Model numbers are usually written as “ Model” or “mod”, then “No.” and then the number. Einige dieser kleinen Ferngläser haben Modellnummer auf den Prismaabdeckungen. Fast alle diese Ferngläser haben Seriennummern. Die Seriennummern werden häufig mit Modellnummer verwechselt. Modellnummer werden geschrieben normalerweise als „Model“ oder „Mod“, dann „No.“ und dann die Zahl. Quelques jumelles affiche des numéros de type sur les couvertures de prisme. Comme presques toutes ont les numéros de séries, les numéros de type sont souvent confondus avec les numéros de serie. Les numéros de types sont souvent prefixe par « Model » ou « Mod », avec ou sans « No. ».

Miniature Binoculars Serial Numbers. Miniatur-Fernglas Seriennummer. Numéro de Série des Jumelles Miniatures. Орядковый Номер. Miniatyr Kikare Serienummer. Miniatura Prism á ticos Número de Serie.

“Reverse Porro Prism ”. Rückwärts Poro Prisma. Jumelles Prisme Inverse de Porro. обратная призма. ポロプリズム. Omvänd Poro Prisma. Omgekeerd Porro Prisma. Prisma de Porro Atrás. Prisma Porro Inverso.

Reverse porro prism binoculars arrange the prisms in a configuration so that the image transmission reverses itself twice, allowing a particularly compact design package. Diese Ferngläser haben Prismen, das den Weg des Lichtes zurück auf sich zweimal dreht. Ces jumelles ont des prismes qui renverse le chemin de la lumière deux fois

In some languages and at various points in times these small binoculars have been referred to in a number of ways. They are  often referred to in English as “miniature binoculars”, or as micro or vest pocket or pocket or compact or mini or spy or skeleton binoculars, or less correctly as opera glasses (true opera glasses are non prismatic). They are also sometimes referred to as field glasses or theater glasses. German nomenclature is also complicated, and subtleties of meaning today might have been less so in the past. For example, while the German “prismenfernrohr” might accurately today only refer to a prismatic type telescope, in the past Zeiss and others sometimes referred to binoculars that way. These small binoculars may be referred to in German as “Fernglas”, “Ferngläser”, “Opernglas”, “Opergucker”,“Feldstecher”, “Prismenglas”, “Theaterglas”, “Fernrohr”, “Mikrofeldstecher”, “Zwergferngläser”, “Prismenfernrohr” or even “Operngucker Skelettfernglas” or “Mikrofeldstecher”. It makes a Google® search for these in German “challenging”. In Swedish these may be “Miniatyrkikare”, and many languages have sub categories for these beyond the basic term for “binoculars”.

Ambiguous Nomenclature. Viedeutiges –Nomenklatur. Nomenclature Ambigue. вусмысленным названия компаний. Tvetydig   Nomenklaturen. Nomenclatura Ambigua.

Serial numbers on the prism covers. Seriennummer auf der Prismaabdeckung. On trouve les numéros de série sur la couverture du prisme.

Serial number on the frame

Almost all of these small binoculars have serial numbers. On some of the earliest it is on the frame, as in the first photo. On post war versions it is normally on a prism cover. Though sometimes confused with model numbers, the serial number is usually longer, and is usually is written as “No.” and then the number. Die meisten dieser kleinen Ferngläser haben Seriennummern. Die Seriennummer ist normalerweise auf der Prismaabdeckung. Es wird als „No“ und dann die Zahl.La plupart de ces petites jumelles ont des numéros de série. Il est normalement sur la couverture de prisme. Cependant parfois confus avec des numéros de type, le numéro de série est plus grandque le nombre de type et est préfixe par « No. ».

Quality Inspection: Binoculars. Qualitäts-Inspektion Fernglas. Inspection de Qualité des Jumelles. Проверка качества.Бинокль. Kvalitesontroll av Kikare. Inspección de la Calidad de Prismáticos. Ispezione di Qualità del Binocolo.

The flyer at right came with one of these binoculars and explains the Japanese “quality” inspection by the JTII (Japan Telescopes Inspection Institute), a quality control organization for optical products being exported from Japan. Various alternate “inspection arrangements” also existed.

Power (Magnification) of Binoculars. Leistung Im Sinne De Ferngläser. Puissance d’optique des Jumelles. оптических измерений мощности на бинокли. Förstoring av Kikare. Potencia óptica de Prismáticos. Ingrandimento del Binocolo.

Most binoculars use a standardized nomenclature to denote power, such as “6x15”. This designates the power and the objective lens diameter in millimeters. So “6x15” is six power using a 15mm objective lens diameter. The power is the magnification, and the larger the number then the greater the magnification. The objective lens is the last lens on the binocular furthest from the eyepiece. Size of this affects the light gathering ability of the binocular, and is also used in designing the field of view of the binocular.

Objective lens diameter

Field of View of Binoculars. Sichtfeld Fernglässer. Champ de Vision des Jumelles. Поле зрения бинокль. Synfält Kikare. Campo de Visión Prismáticos. Campo di Vista del Binocolo.

Field of view is how much the binocular can see right to left, expressed as an angle, or alternately expressed as how many feet right to left can be seen at 100 yards. The photos below illustrate the difference between an Asahi made Bushnell 6x25 (‘wide angle”) binocular and an Asahi made Bushnell 6x15 binocular. Same power (6x), same manufacturer, but different lenses and prisms, and quite a different result in the image produced. (Photos are a simulation of the binocular view)

Photo of some of the Land Rovers I dragged out of the weeds and rebuilt myself for my collection, less a diesel that wouldn’t start on this day, less one I sold, and less one I wore out (and less two un-restored and immobile) Photo using wide angle lens by Jim Leach. Also the approximate view one sees using the Bushnell 6x25 wide angle binocular at 150 feet, which has a comparatively wide field of view.

Same magnification.

Same brand.

Different objective lenses.

Different prisms.

Different geometry.

Different field of view.

This is the approximate view through the Bushnell 6x15 binoculars at the same 150 feet. Lots of Land Rover trucks now missing (and not even from breaking down). Comparatively narrow field of view.

Binoculars or Opera (Theater) Glasses ? Fernglässer Oder Opernglässer?  Jumelles ou Jumelles Theater? Kikare Eller Teater Glasögon ? Prismáticos o Lentes de Teatro? Binocoli o Occhiala da Teatro?

   There is often confusion about what is properly an “ opera glass ” or “ theater glass ”, versus a small (prism) binocular . There is a specific difference that is based on the type of lens configuration and lens arrangement.

    Opera glasses and theater glasses use Galilean optics. That is to say they use a concave eyepiece lens and a convex objective lens mounted in-line to produce an inexpensive and simple low power magnified image by direct transmission, but which is correctly oriented due to the combination of lenses. They do not use prisms. The eyepiece (ocular lens) is in line with the last (objective) lens. The performance is inferior to prism binoculars, and the magnification normally low.

   The small binoculars on this website use four porro prisms (triangular prisms that each shift the image path 180 degrees) to create a correctly oriented image, plus magnification lenses. The image path reverses itself twice, and these binoculars are poro prism binoculars , and to be more technical, are  reverse porro prism binoculars.  This prism arrangement also gives a compact configuration. The eyepiece (ocular lens) is offset to the last (objective) lens.

Text Box: Text Box:

Opera glasses

Reverse Porro Prism Binoculars

Prism Glass: BaK4 and BK7 . Glasmaterial BaK4 und BK7. Jumelles Prismes BaK4 et BK7. Стекло формул, h используемых на призм: BaK4 и BK7. Prism Glas: BaK4 och BK7.Cristal Las Fórmulas Utilizadas en los Prismas: BaK4 y BK7.

One sometimes encounters the binocular prism designations BaK4 and BK7. These originally were designations created by Schott AG for it’s optical glass products. BaK stands for Ba ritleich K ron or Barium Crown glass. Schott AG Bak4 is a specifically defined glass: # 569561 glass with a refractive index of 1. 569 and an Abbé number of 56.1 , which indicates how much it will disperse light into its component colors. And Schott AG BK7 indicates the use of borosilicate flint glass. But because these are products and designations of a private company and not a publically defined or enforced defined standard, Bak4 marked optical glass made be phosphate crown glass. In theory Bak4 has a high refractive index, and will pass more light on the edges of the field of vision. But because of hype and promotional misuse of the designation by optical distributors, and because quality and performance are the totality of a great many factors rather than just the glass, these designations as used in the general consumer market may mean little or nothing as a prediction of the actual performance or quality of a pair of binoculars. BaK4 ist hochwertiges glasmaterial aus Bariun-Kronglas. BK7 ist glassorte aus Bor-Kronglas mit guten transmissionseigenschaften. Bak4 Vidrio es Bario Vidrio. Bk7 Vidrio es Borosilicato Vidrio Flint.

JTII (Japan Telescope Inspection Institute at work inspecting binoculars, in the 1950’s.

Die Geschichte betreffend Miniaturferngläser in Japan.

L'histoire des jumelles miniatures au Japon

De geschiedenis van piepkleine verrekijker in Japan

日本 の小型双眼鏡の履歴

Historien om miniature kikkert i Japan

La historia de Japón los prismáticos en miniatura

История в отношении японского миниатюрного бинокль

Η ιστορία των μικροσκοπικών κιάλια στην Ιαπωνία.

Historie ohledně japonských miniaturní dalekohled

La storia in miniatura binocolo in Giappone.

The manufacturers Omori Sogo, Meiji Seiko, Tokuhiro, Akebono, Tochihara, & Tanaka all also produced binoculars under similarly long lists of brand names. The interplay of brands and models and makers makes these appealing little binoculars a lot of fun, and they are also practical precision optical devices that work quite well (at least when in a good state of repair) in virtually the same form as when first invented 99 years ago.





Berkeley Scientific











Frank Nipole

Gold Crest

Gold Cup

Golden Gate





Hi Score

HK Ideal









Karl Stein






Mt Fuji


























Super Zenith




This prism arrangement gives a visually correct image, rather than an upside down or mirrored image.

Yellow Warning Sign U-turn Roa... Yellow Warning Sign U-turn Roa...














Precision optical glass production process

Photo credit: Lytkarinsky Optical Glass Factory

The following list is of manufacturers I have observed to have been involved in the manufacture of the many various brands of these Japanese (miniature) External Reverse Porro Prism Binoculars, either as the assembling manufacturer of record (JB number), or as the parts manufacturer of record (JE number), or as an identified subcontracting manufacturer or manufacturing distributor. Please note that some manufacturing efforts in the 1950’s and 1960s were essentially consortium group efforts so that there were almost certainly many other manufacturers in addition to the assembling and/ or parts manufacturer of record. So the list should be regarded as accurate but incomplete. Where possible the companies are listed in their “translated” form, and in rōmaji, and in Kanji (see the section “ Understanding the Name Variations ” on the page ” INTRODUCTION ” for a complete explanation). Addresses, where available, are normally from a 1959 list of binocular makers published by the Japan Binoculars Export Promotion Co and made available by Peter Abrahams at:

http://home.europa.com/~telscope/j-list.txt  Be aware that if a company had more than one location at the time, then this address is probably a sales office address, rather than a factory address, but it could be either.


Akebono Optical Co., Ltd. (Akebono Kōgyō Seisakujo) ( 曙光学工業 ) : 1-956 Nogata-cho, Nakano-ku, Tokyo

Asahi Optical Co.Ltd. ( Asahi Kōgaku Kōgyō Kabushiki-geisha) ( 旭光学工業株式会社 ) 980 Shimura-maeno-cho, Itabashi-ku,Tokyo

Asanuma & Co Ltd

Carton Optical Industries Ltd ( カートン光学株式会社)

Fuji Photo Optical Co,. Ltd. : 1-24 Uetake-cho, Omiya-Shi, Saitama

Furukawa Kōgaku Seisakujo ( 古川光学製作所 )

Hoya Optical Co, Ltd. (Hoya Kōgaku Kōgyō Kabushiki-geisha) ( 保谷光学株式会社 ) 38 Oyama-Kanai-cho, Itabashi-ku, Tokyo

Ibuki Kōgaku Co. Ltd.   ( 伊吹光学株式会社 )

Iikura Optical Works (Iikura Kogaku Seisakujo Inc.) ( 飯倉光学製作所 ) : 43 Tokumaru-cho, Itabashi-ku, Tokyo

Kamakura Optical 2-51-2 Shimo-machi, Kita-ku, Tokyo

Kuroki Kogaku Kogyo Co, Ltd.

Meiji Seiko Co, Ltd. ( 明治精工株式会社 ) : 803 Yukigaya-cho, Ota-ku, Tokyo

Nikkei Optical Co. ( 日経光学株式会社 )

Nippon Kogaku Kogyo Co.Ltd. (Nippon Kōgaku Kōgyō Kabushiki-geisha) ( 日本工学株式会社 )Oi-Morimae-cho, Shingawa-ku, Tokyo

Oei Kōgaku Co Ltd. ( 応永光学株式会社 )

Ofuna Optical Instrument Co., Ltd (Ofuna Kōgaku K.K.)( 大船光学工業株式会社 ) 659 Dai, Kamakura-shi, Kanagawa

Oji Optical Machine Co. Ltd (Oji Kōgaku Kikai K.K.)( 王子光学機械株式会社 ) 5-34 Inatsuke-Nishi-machi, Kita-ku, Tokyo

Okaya Optical Co, Ltd (Okaya Kōgaku Kikai K.K.) 岡谷光学機械㈱ ( Vista brand binoculars)

Omiya Kōgaku Kikai Seisakujo ( 大宮光学機械製作所 )

Omori Sogo Kōgaku Kōgyō Ltd. ( 大森総合光学工業 ) : 202 Ikegami-Honcho, Ota-Ku, Tokyo

Oshimoto Kōgaku Co Ltd

Otake Optical Co (Otake Kōgaku Kōgyō Kabushiki-geisha( 大竹光学工業株式会社 )  

Pentax Corporation (Pentakkusu Kabushiki-geisha )( ペンタックス株式会社, )

Rikken Optical Co., Ltd. (Riken Kōgaku Kōgyō K.K.) ( 理研光学工業㈱ )

Sankyo Optical Co Ltd.   (Sankyo Kōgaku Kōgyō Kabushiki-geisha) ( 三共光学工業株式会社 ) : 2-8 Naka-Jujo, Kita-ku, Tokyo

Siewa Optical Co. Ltd. (Seiwa Kōgaku Kōgyō Kabushiki-geisha ) ( 清和光学株式会社 ) : 5-1617 Naka-machi, Nerima-ku, Tokyo

Tanaka Optical Co Ltd (Tanaka Koki Seisakujo) ( 田中光機製作所 ) 4 Fujimi-cho, Itabashi-ku, Tokyo

Toa Optical Co., Ltd. (Toa Kōgaku Kōgyō Kabushiki-geisha )( 東亜光学株式会社 ): 1-7 Chihaya-cho, Toshima-ku, Tokyo

Tochihara Optical Co ( 栃原光学株式会社)

Tokuhiro Micro Binocular Co : (Tokuhiro Koki Seisakusho Inc)( 徳弘光機製作所株式会社 )9-1101 Nippori-machi, Arakawa-ku, Tokyo

Ueta Seiki Co. Ltd

Yashica Co Ltd ( Yashica Kōgyō Kabushiki-geisha ) ( ヤシカ ) plus U.S. subsidiary marketing firm Yashica Inc.

Yoshimoto Optical Co Ltd. : ( 吉本光学株式会社 ) 1-3340 Nishi-Sugamo, Toshima-ku, Tokyo

Zuiho Optical Instrument Co Ltd. ( Zuihō Kōgaku Seiki K.K., Tokyo )( 瑞宝光学精機工業株式会社 ) 3-7 Kyobashi, Chuo-ku, Tokyo



Japanese Companies Involved in the Manufacture of Miniature Binoculars. さな日本双眼鏡生産する企業 . Japanische Firmen die Miniaturferngläser Herstellten. Sociétés Japonaises Qui Ont Fait les  Jumelles Miniatures. Японские компании, вовлеченные в производство миниатюрных бинокль. Las Empresas Japonesas Involucradas en la Producción de los Prismáticos en Miniatura. Aziende Giapponeisi Coinvolte Nelia Pruduzione de Binocoli Miniatura.

What Are Miniature External Reverse Porro Prism Binoculars? Was sind Miniatur-externe Porro-Prismen-Ferngläser?Quels sont les jumelles miniatures externes de prisme de prisme inversé? ミニチュア外部逆ポロプリズム双眼鏡とは何ですか? Vad är Miniature Extern Reverse Porro Prisma Kikare?Wat zijn miniatuur externe omgekeerde Porro Prism-verrekijkers?¿Qué son los prismáticos de prisma de Porro reverso externo en miniatura?Che cosa sono i binocoli con prismi a porro rovesciati esterni miniaturizzati?

They are compact porro prism binoculars with the prisms “reverse” positioned so that the objective lenses and barrels are closer together than the oculars (eyepieces) to make them more compact than standard proro prism binoculars designs, and with the prisms in 4 separate “external” prism covers rather than being mounted internally within a single piece housing or body. Binoculars are generally classified by presence of absence of prisms, and how they are arranged, as shown below. Sie sind kompakte Porro - Prismen - Ferngläser, deren Prismen "reverse" so positioniert sind, dass die Objektivlinsen und - trommeln näher beieinander liegen als die Okulare (Okulare), um sie kompakter als herkömmliche Proroprismenferngläser zu machen, und die Prismen in 4 separaten "externen" "Prismenabdeckungen, anstatt dass sie intern in einem Gehäuse oder Gehäuse aus einem Stück montiert sind. Ferngläser werden im Allgemeinen durch das Vorhandensein von Prismen klassifiziert und wie sie angeordnet sind, wie unten gezeigt. Ce sont des jumelles prismatiques compactes avec les prismes "inversés" positionnés de telle sorte que les lentilles et les objectifs sont plus rapprochés que les oculaires (oculaires) pour les rendre plus compacts que les modèles proro prismatiques standard, et avec les prismes dans 4 "Le prisme recouvre plutôt que d'être monté intérieurement à l'intérieur d'un boîtier ou d'un corps monobloc. Les jumelles sont généralement classées en fonction de l'absence de prismes et de leur disposition, comme indiqué ci-dessous





Serial Numbers on Miniature Binoculars. Seriennummern auf Miniatur–Fergläsern. Numeros de Série Sur des Jumelles Miniatures. Serienummer På Minikikare. N ύ meros de Series en Prismatáticos Miniatura. Numeri Seriali sul Binocolo in Miniatura.

Serial numbers can be useful in suggesting where in a production run a particular pair falls, or when changes in designs occurred relative to each other. But they can also be potentially misleading. Serial numbers can be assigned from number one for each brand or for each individual model, or for everything the company made, or could be assigned as a specific block for a particular model, so that serial number 20,213 could actually represent binocular #213 produced of a type assigned a serial number block starting at 20,000. That would also mean that serial number 20,213 did not really represent 20,213 of anything having been made, absent observation of other earlier serial numbers. We know that some of the Baumann binoculars (Fata Morgana 6x, Optistar6x) worked that way, but the Fata Morgana 4x presumably started at serial #1. That type systems means numbers in between blocks might never have been actually placed on a product. Serial numbers could be assigned to represent an actual manufacturer’s number, regardless of the various brand contracts that a manufacturer might produce, or could be assigned from #1 for each brand contracted with an importer or exporter. With low numbers or with a serial number spread of examples of identical binoculars to examine, a good educated guess might be possible as to how the serial numbers were used. Additionally, manufacturers sometimes start preproduction prototypes at serial number 1, but then start production numbering at an artificially higher number, to counter the widespread [and sometimes correct] public perception that early production runs of anything don’t really have the bugs worked out. So it is probably risky to make quick definitive assumptions based on serial numbers absent a number of examples to give a better idea of how the numbers were being used .

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