Miyagawa Seisakusho (宮川製作所) was a Japanese company from as early as 1935. It made the Picny 3×4 camera and the Boltax and Bolty cameras using Bolta film. It is called Miyagawa Seiundō (宮川星雲堂) in the April 1943 government inquiry on Japanese camera production; its address at the time was Tōkyō-to Nakano-ku Kami-chō 131 (東京都中野区上町131).
The company survived the war. It perhaps made the Silver, a continuation of the Boltax with auto-stop advance. In 1948, it released the Picny B, a redesigned camera taking Bolta film. The Picny 35 and Royal 35 were derivatives taking perforated 35mm film. Miyagawa perhaps also made other cameras called Royal before disappearing.
- "Kokusan shashinki no genjōchōsa" ("Inquiry into Japanese cameras").
- 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.
- "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.
- 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.