The adapter is very thin, made out of two metal layers. The metal lens mount ring is silver and is friendly to Nikon mount. The metal mount behind the lens ...
Step-by-step instruction on making a Canon EOS pin-hole lens. Same steps may be followed for other camera systems.
I saw this hack. It involves grinding the spacer on the lens and taking out the MD mount and putting on the EOS mount (from a m42->EOS adapter). Looks like ...