I've got a couple of Industar-50 lenses, but on FSU SLRs (a Zenit C and a Kristall), not on a rangefinder. It's a pretty good lens, but not the best I've seen of that focal length -- at least, the one I compared directly to other lenses wasn't. Actually, I slapped together a Web page with my comparisons. Keep in mind these weren't exactly laboratory controlled experiments. Things like chance camera shake or bad focus could have thrown the results off. (I did use a tripod and cable release, though.)

Karen Nakamura has a Web page on this camera. Another useful resource is the Zenit Camera Group on Yahoo. (Don't be thrown by the name; they welcome discussions of any Russian/FSU cameras or lenses. Zorkis are definitely on-topic there.)