The Japanese government inquiry listing camera production as of April 1943 has an Osuten Refu (オステンレフ), listed among TLR cameras. All the TLRs mentioned in this document are called "Ref" (レフ) instead of "Flex" (フレックス), for example the Elmoflex is listed as the "Elmo Ref" (エルモレフ) and the Minoltaflex as the "Minolta Ref" (ミノルタレフ). The name Ostenflex, from the German word Osten meaning East, is conjectural only.
The document mentions an Osten (オステン) shutter giving 1–300, B speeds and made by Tōa Kōki. The lens is given as a three-element Grimmel 75/3.5 made by Fujita Kōgaku Kikai, the same as on the Semi Gelto and Gelto Six. Unfortunately, the name of the maker and distributor are missing from the listing, but the lens and shutter equipment seems to point at Tōa Kōki.
The camera is not listed in the official list of set prices compiled in October 1940 and published in January 1941. It was thus not yet produced at the time.
No surviving example and no picture has been observed so far.
- "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. Item 122.
- "Kokusan shashinki no kōtei kakaku" (国産写真機の公定価格, Set prices of the Japanese cameras), listing Japanese camera production as of October 25, 1940 and setting the retail prices from December 10, 1940. Published in Asahi Camera January 1941 and reproduced in 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. Pp.108—9. The camera does not appear in this document.