Originally posted by Aaron28 lentar 135/f2.8 T-mount (which I though was m42 because that's the adapter that was on it)…..K-50
Those adapters can be tricky. I bought a medium format Pentacon 6 lens, the Arsat 30 f 3.5 fisheye, which the seller insisted had a Pentax 645 mount. I had never heard of a P645 mount on this lens, so bought it suspecting that it would arrive with a P6-P645 adapter, which in fact proved to be the case. Fine with me as I would otherwise need an adapter to use the lens on the 645Z. However, the adapter was fitted on so tightly as to require special measures for removal!