This is a body cap to fit the Contax-Yashica CY-Mount. It uses the standard locking pin in the camera to latch in place, so to release you must hold down the lens release button.
Knurled edge to help in attaching/detaching from the camera. My first prototypes had a smooth circumference, and that made it very difficult to grab onto.
Tested on Yashica FX-2 camera and also a CY to Sony E-mount adapter.
I recommend printing with support because of the bayonet flanges.
The author marked this model as their own original creation. Imported from Thingiverse.