Time to look at another Russian beautie :)
Today's model was born in 1958 in the KMZ plant in Krasnogorsk, which also fathered the Zorki and Zenit brethren. The Industar-50 (ИНДУСТАР-50) has many incarnations. In its first life, starting in 1953, the Industar-50 was a collapsible lens, very much like the leicafamous Elmar, but already during the 1950s reincarnated as a rigid lens. Several types of the rigid version have been described. This shiny aluminium beauty is one of the more common types. Princelle lists it as K440.
Aperture range: f/3.5-f/16
Minimum focussing distance: 1m
Aperture blades: 8
The П-mark (Просветление, which can be translated as "enlightenment") indicates that coating was applied.
The ARG-file I use with exiftool: industar50f35rig_5808420.txt
-EXIF:LensModel=Industar-50 5cm f/3.5 Π (M39)
This works for LR4 and NEX-5 RAW-files.