M42 adapter rings

Some adapter rings, to fit my M42 screw-mount lenses on bayonet bodies.

At left, for Minolta MD, on the right for Pentax K. Found in customer's “dustbins”.

And here rings for Praktica B, those on the left from Praktica origin, including the one I bought for my first B200, 3 others recovered at customers'. I bought the one on right-hand side (Hama) to arrange it (to plane the cap of the electrical contacts) to be able to use the Helios 40 (1.5/85mm) which basis is too broad to be screwed home on a normal ring.

Lacking on this page: the M42-Canon EF ring (on the page of Canon FTb), and the M42-K special rings of Zenit Automat and AM.