Green Camera Works c1950
The Green camera produced by Green Camera Works in Japan is perhaps one of the rarest cameras to be found. No references can be found on this camera except McKeown who indicates that the camera was produced about 1950. However, the Pisco shutter found on this example was apparently used on several other post-WWII Japanese cameras such as the Kiko 3 and Semi Rody, both produced for a brief period after WWII.
Similar to many inexpensive Japanese cameras intended for western markets immediately before and after WWII, the Green camera was produced only for a brief period. Aside from this source, little information is available on the Interenet regarding the Green Camera Works. However, it is evidently a name variant of the Gotex, a 6x6 camera made by Kigawa between 1941 and May 1945 when the production facilities suffered damage from bombing (for more information see the article by Tatsuo Shirai in "The History of the Japanese Camera", and http://camerapedia.org/wiki/Gotex_and_Poppy_Six).
This example produces 6x6 cm images on 120 film. It's horizontal folding bellows design is similar to a number of German designs popular in pre-WWII Japan. It has a coated 75mm f/3.5 Green Anastigmat lens and a Pisco shutter providing 1 sec through 1/250 sec, B and T settings.
The rear door has a film window with a cover engraved with KKS but it is not evident to which company it refers. It is likely that it refers to a small, possibly non-existent company which was rather common in the Japanese camera market of the early 1950's. Die cast camera bodies could be purchased frequently from small operations that even used cast-off old dies and components from other companies. In post-war Japan, a three element 75mm f/3.5 lens could be purchased from small unknown manufacturers for as little as ¥300 including a personalized name. The "Green Anastigmat" lens seen on this camera may be an example .
A vast production of very poorly made cameras in the early 1950's led to the formation of the Japan Camera Inspection Institute, or JCII which is widely recognized today as the entity responsible for maintenance of the remarkably high production standards in Japan. This continues to be one of the most obscure and curious cameras in the collection.
The KKS mark on the back of the camera probably refers to a small unknown, or possibly even a non-existent company.
I would encourage you to read The History of the Japanese Camera published by the JCII (see References and Acknowledgements).