test the lens outside on a sunny cloudless day... crank the lens to its highest aperture, and set your focus to infinity. crank the photo and see if the dust shows up in the picture. if it does, then buyer beware.
if it doesnt end up showing, make sure that you understand that the resale value of this lens will definitely go down.
Well, I tried to shoot plain paper sheet from close (focus to infinity) at f/22 and besides some normal small dust spots nothing else seems to appear in the picture. I wonder how the dirt would influence lens behaviour in contrejour lighting. Good point with the resale value. I think I'll just wait for some other deal to appear.











