At least three Japanese camera-related companies were called Sankō.
Sankō Shōkai[]
Around 1942, a company called Sankō Shōkai (三光商会) and based in Tokyo, Ginza distributed the Oko Six and Oko Semi made by Ōki Kōgaku Seiki Seisakusho.
Sankō-sha[]
In 1943, a company called Sankō-sha (三光社) and based in Tokyo, Asakusa offered rangefinder conversions for the Gelto, Arsen, Picny, Boltax, Roico and Molby. It was also mentioned in the April 1943 government inquiry as the distributor of the Cyclon, a 3×4cm camera with perhaps a focal-plane shutter.
K.K. Sankō[]
Baby Suzuka
Between 1951 and 1954, K.K. Sankō (㈱三光), based in Tokyo, Taito made or sold the Baby Suzuka 3×4 camera. A company called Sankō K.K. (三光㈱) exists today (2007), and currently makes chemical products. It was founded as Sankō Shōkai (三光商会) in 1946 and became Sankō K.K. in 1949, so it might be the same company.
The relationship between all these companies is unknown.
Other[]
The Sun subminiature pseudo TLR has a Sanko 35mm lens, and the Baby Flex has a Sanko 20mm f/3.5. The origin of these lens names is completely unknown.