I recently bought a used Zeiss Tessar from a New York photostore on ebay. They have a shop in NY and seemed to be on the level. I wasn't the happiest about buying something I haven't examined by hand, but I've found Zeiss lenses from the 30s-50s to be nearly impossible to find here in DC.
However, I've read a wide range of things on used lenses. The lens I got was about $40 and is the original equipment (even proper vintage it seems) for my old Exakta. I've read a wide range of things about used lenses ranging from leaky oil problems to fungus growing inside. The lens arrives this week and I'm wondering what your thoughts on it are. Should I put it out in the sun in case there is some kind of fungus inside (there isn't suppose to be according to the seller who graded it in "excellent" condition but I don't want to take any chances with something that can spread about)? If so how should I do that? Is there a clean up you recommend when it arrives before I put it on the camera? I figure it may need a slight external cleaning to prep it, right? Any other thoughts on used lenses?