I've listed an Industar-10 50mm f3.5 collapsible lens, in great condition, with the original metal lens cap, original “FED” storage case, a Russian M39 macro extension tube and a Russian M39 rear cap. My best guess, based on Princelle’s “Authentic Guide to Russian and Soviet Cameras, 2nd Edition”, is that this particular lens was manufactured in the early to mid-1950s. If you read my Industar Collapsible 50mm Comparison, you know that I think the Industar-10 is the best of the Industar-10/22/50 family. This particular example has the added benefit of a unique design to the infinity lock, which means the lens can be used on an adapter with no modifications. Thanks for looking - cheers!