The Industar 61, produced at the FED factory in Kharkov, Ukraine. It is a "normal" lens for M39 (Leica screw mount) and M42 (Pentax screw mount), with a focal length from 53-55mm, depending on the production run. Its six-blade iris provides a range of apertures from f/2.8 to f/22.
The Industar 61 L/D is possibly the most highly regarded lens for Ukrainian Leica copies. In an L/D or L/Z version of this lens, the L indicates that the lens has Lanthanum in it, and D indicates M39 mount while Z indicates M42 mount.