I had a 44M lens on my Zenit SLR in the late 70s. Good lens for a real budget camera although, as you probably know, it loses its sharpness around the edges. The only anecdotal pointer I can give you is that the ballbearings in the focus ring failed, which Zenit's UK importer sorted for me no questions asked. So, when you get one, check that the focus ring turns smoothly. I'm assuming that it applies equally to the 44-2. What serial # is best? Gosh, that's a bit geeky even for a specialist camera forum (which this isn't). Best of luck, though; they're all pretty much in the £20-35 range and getting some inside knowledge could help you pick up a sleeper.