Originally posted by stevebrot Very strange. The lens pictured is a rangefinder lens that appears to have had its rear section replaced by who knows what. You can't just replace the Helicoid to magically transform a short registration lens into one that will work on a SLR. The telling photo is the one with the silver and black lenses together as well as the sample photo. The silver is an unmodified Heliar the black is the offered lens. I suspect that the rear group has been removed.
I would suggest that potential buyers consider finding the VC 74/2.5 SL in Pentax K instead.
Steve
Yes Indeed, It seems it used to be an L-mount m39 given a M42 conversion, which explains the loss of the distance markings in the process. I asked the seller about the conversion and he told me that he bought it converted for his sony Nex years back.
I recently bought a Voigtlander Color Ultron 50mm f1.8 from this seller, and I'm very happy with it.
It looks like the second one from the left in this picture i pulled out