Kōyō Shōji (厚用商事) was a Japanese distributor in the first half of the 1950s. It sold the Crown Flex 6×6 TLR in 1953, certainly made by Kobayashi Seikō, and gave its name to the Kōyō Anastigmat lenses mounted on this camera.
- 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.