Earth Kōgaku K.K. (アース光学㈱) was a Japanese company based in Tokyo in the late 1930s and early 1940s. Before getting into camera production, the company was making a pocket monocular. In 1938, it released the Guzzi subminiature camera distributed by Sanwa Shōkai. It also made the Loren 3×4 folder from about 1940. On the cameras, the company name was displayed as EARTH KOHGAKU or EARTH K.K.
After 1945, the Guzzi was revived as the Top, ostensibly made by Top Camera Works; it is not known if this was the name of an actual company, maybe a successor to Earth, or a mere dummy name for Earth Kōgaku.
- Its address in 1938 was in Nihonbashi-ku (日本橋区); source: column in Asahi Camera June 1938 reproduced in Awano, p.7 of Camera Collectors' News no.277. In 1943 it was Tōkyō-to Mukōjima-ku Azuma-chō Higashi 3123 (東京都向島区吾嬬東3123); source: "Kokusan shashinki no genjōchōsa" ("Inquiry into Japanese cameras").
- Column in Asahi Camera June 1938 reproduced in Awano, p.7 of Camera Collectors' News no.277.
- Asahi Camera (アサヒカメラ) editorial staff. Shōwa 10–40nen kōkoku ni miru kokusan kamera no rekishi (昭和10–40年広告にみる国産カメラの歴史, Japanese camera history as seen in advertisements, 1935–1965). Tokyo: Asahi Shinbunsha, 1994. ISBN 4-02-330312-7.
- Awano Mikio (粟野幹男). "Gucchī" (グッチー, Guzzi). In Camera Collectors' News no.277 (July 2000). Nishinomiya: Camera Collectors News-sha.
- "Kokusan shashinki no genjōchōsa" (国産写真機ノ現状調査, Inquiry into Japanese cameras), listing Japanese camera production as of April 1943. Reproduced in Supuringu kamera de ikou: Zen 69 kishu no shōkai to tsukaikata (スプリングカメラでいこう: 全69機種の紹介と使い方, Let's try spring cameras: Presentation and use of 69 machines). Tokyo: Shashinkogyo Syuppan-sha, 2004. ISBN 4-87956-072-3. Pp.180–7.
- 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.253.