Help me identify this lens?

[smithdan]

Hard to see from your pix if this lens has an auto-manual switch. If not, and I may be mistaken, just going on my experience, it can be only shot wide open. Adapters will change the lens to the appropriate mount and manage most optical differences but the stop down pin system was pretty much unique to M42 mount cameras. As for Vivitar, I've found that their performance is hit and miss.