>>3417067>>3417068>>3417069The OP picture shows a M39 mount _SLR_ Industar-50 with an incorrect description. NOT a rangefinder lens, NOT a M42 SLR lens.
It can only be adapted to a digital camera if you have 2 adapters - M39 to M42 ring, and a M42 to whatever mount adapter. Direct adapters do not exist because the confusing M39 SLR mount was only used by very early Zenits and no other camera in the world.
<-- Industar-50s for M39 rangefinder mount are either collapsible, or look like this.