The Gemmy is shaped as a pistol. The main body has a cream and chocolate two-tone lacquer finish, and the metal fittings are chrome plated. The camera takes 10×14mm exposures on 16mm perforated film loaded in two cassettes, similar to and perhaps compatible with the cassettes of the Mamiya 16. They are contained inside the handgrip, whose right-hand panel is hinged at the bottom and locked by a sliding button at the top. The left-hand side of the handgrip is fixed and has the name GEMMY embossed in relief. There is what looks like a tripod thread at the bottom.
There is no proper viewfinder, but it seems that two sights are hinged at the top of the main body. The trigger both advances the film and fires the shutter, increasing the similarity with an actual pistol. The fixed-focus lens is located at the pistol's muzzle — some sources report that it has 35mm focal length. The shutter gives 25–100 speeds, selected by an index at the top, and the aperture is adjustable from 4.5 to 11, via another index on the right-hand side of the lens barrel.
The Gemmy was developed by the Okada company, maker of the Waltax. The company changed its name to Daiichi Kōgaku no later than December 1951, and the Gemmy was manufactured before that date. It is said that it was developed by Ishiwata Shigeo (石渡茂雄), the designer of the Kolt, a straightforward subminiature, and of the unconventional Camera "A" and Camera "B".
Research on pistol-shaped cameras started in Japan in the late 1940s, certainly instigated by the police forces. The intended use was to catch photographic evidence of criminal behaviour in the act. The Gemmy was among the first such cameras; it was only produced in limited quantities and it is not known if it was actually used by the police. Other early examples are the Seiki 16 pistol camera, made around 1950, and the Doryu 1, completed in 1952, which remained at experimental level. The Doryu 2-16 and Mamiya Pistol correspond to the second generation of pistol-shaped cameras. These were developed after the incidents of May Day 1952, mostly to take photographs of protesters during demonstrations. The police finally adopted the Mamiya camera in 1954, but it saw only limited use.
- Date: Sugiyama, item 5041, McKeown, p.745, and this page at submin.com.
- Exposure size and film format: Sugiyama, item 5041, McKeown, p.745, Yazawa, p.11 of Camera Collectors' News no.233, and this page at submin.com. Only the latter mentions compatibility with the cassettes of the Mamiya 16.
- Only the rear sight is visible on the example pictured in Sugiyama, item 5041, and the example pictured in this page at submin.com seems to have lost both sights, but two hinges are clearly visible.
- Advances the film and fires the shutter: Sugiyama, item 5041 (in the Japanese text only), Yazawa, p.11 of Camera Collectors' News no.233. Western sources such as McKeown, p.745, and this page at submin.com, only say that the trigger advances the film.
- 35mm focal length: McKeown, p.745, and this page at submin.com.
- Speed and aperture range: Sugiyama, item 5041, and this page at submin.com. Only the speed range is given in McKeown, p.745.
- Yazawa, p.11 of Camera Collectors' News no.233.
- An article in Shashin Kōgyō March 1955 states that the Doryu company started to develop pistol-shaped cameras in 1949, with official support of the concerned authorities (see Doryu 1 and Doryu 2-16).
- See Mamiya Pistol.
- Awano Mikio (粟野幹男). "Tokushū: Mame kamera ni tsuite" (特集・豆カメラについて, Special: On subminiature cameras). In Camera Collectors' News no.31 (January 1980). Nishinomiya: Camera Collectors News-sha. (Pictures on the front and back cover.)
- McKeown, James M. and Joan C. McKeown's Price Guide to Antique and Classic Cameras, 12th Edition, 2005-2006. USA, Centennial Photo Service, 2004. ISBN 0-931838-40-1 (hardcover). ISBN 0-931838-41-X (softcover). P.745.
- Sugiyama, Kōichi (杉山浩一); Naoi, Hiroaki (直井浩明); Bullock, John R. The Collector's Guide to Japanese Cameras. 国産カメラ図鑑 (Kokusan kamera zukan). Tokyo: Asahi Sonorama, 1985. ISBN 4-257-03187-5. Item 5041.
- Yazawa Seiichirō (矢沢征一郎). "Renzu no hanashi (143) Kamera 'A'" (レンズの話カメラ'A', Lens story  Camera 'A'). In Camera Collectors' News no.233 (November 1996). Nishinomiya: Camera Collectors News-sha. Pp.11–5. (On Ishiwata Shigeo.)
The Gemmy is not listed in Kokusan kamera no rekishi.