The Semi Oscon is a vertical folder with a die-cast body. The top housing is placed on the right, as seen by the photographer holding the camera vertically, the reverse of the usual arrangement. The body release is tripped by the right hand's finger. The Semi Oscon has automatic stop advance. The advance knob is at the left end, near the folding bed release button, and it seems surrounded by an exposure counter.
The viewfinder protrudes from the top housing; it is slightly offset to the left. Above the viewfinder is a folding sports-finder, with a bar in the middle of the front frame. There is an accessory shoe to the right of the finder and a dial on the right of the top plate, which seems to be a film reminder. The back is hinged to the right.
The folding struts are engraved with a YK logo (certainly for Yamagata Kikai), and an Oscon nameplate is screwed to the front of the body. The name Oscon is embossed in the leather case too.
The camera was advertised by Ōsawa Shōkai in August, September and December 1953, together with the Primoflex or Topcon 35 cameras made by Tōkyō Kōgaku. The advertisements ambiguously suggest that the Semi Oscon was made by this company too, and they do not mention Yamagata. (For example, in this advertisement dated 1954, reproduced in the Shashin-Bako website, we read the following: "Applaused cameras by Tōkyō Kōgaku, representing the Japanese optical world", translation of "日本の光学界を代表する東京光学の絶讃カメラ"). This is obviously intentional: Tōkyō Kōgaku was a reputed company whereas Yamagata Kikai was virtually unknown.
- Dates: articles and advertisements listed in Kokusan kamera no rekishi, p.348.
- Attribution to Yamagata: Kokusan kamera no rekishi, p.348, Lewis, p.79, Sugiyama, item 1381. Affiliated with Tōkyō Kōgaku: See the chronology of the Topcon official website and the chronology of the Topcon Yamagata official website. Lewis, p.79, Sugiyama, item 1381, and Tanaka, p.79 of Kurashikku Kamera Senka no.8 say that Yamagata Kikai was related to Nippon Kōgaku, certainly by mistake.
- Sugiyama, item 1381.
- Advertisements published in Asahi Camera, reproduced in Kokusan kamera no rekishi, pp.124 and 175.
- 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. Item 433. (See also the advertisement for items 785–6.)
- Lewis, Gordon, ed. The History of the Japanese Camera. Rochester, N.Y.: George Eastman House, International Museum of Photography & Film, 1991. ISBN 0-935398-17-1 (paper), 0-935398-16-3 (hard). P.79.
- 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 1381.
- Tanaka Masao (田中政雄). "Sonota no nihon no supuringu-kamera" (その他の日本のスプリングカメラ, "Other Japanese folding cameras"). Kamera Rebyū: Kurashikku Kamera Senka (カメラレビュー クラシックカメラ専科) / Camera Review: All about Historical Cameras no.8, September 1986. No ISBN number. Supuringu kamera (スプリングカメラ, special issue on spring cameras). Pp.76–80.
- Advertisement for the Semi Oscon, Primoflex and Topcon 35, published in 1954, reproduced in a page of Japanese postwar advertisements at the Shashin-Bako website