Today, I pulled the trigger on a couple of interesting new additions to my Soviet lens collection... A Jupiter-38 4/75 and Jupiter-39 5.6/135 in M42 mount.
They were designed for use with a Russian Selena 35mm traffic police camera which (from what I've learned online) ultimately proved unsuccessful, and production was therefore rather limited. These lenses are quite scarce, but come up for sale every now and then individually, as a pair, or as part of a complete kit including camera, viewfinders, filters, film reels and cassette, in a purpose-built case. From what I can glean, the flange focal distance is the same as for M42-mount SLRs. The 135mm is based on a Sonnar. Not sure about the 75mm... another Sonnar, or perhaps a Biotar?
I'm waiting for these to arrive from Russia, probably in 8 - 10 days time. Until then, seller's photo below... Jupiter-39 on the left, -38 on the right