...you can do all the tests you want, but if you sold that camera to me and the shutter speeds were off or the back wasn't giving even spaces, I'd be pissed. Let someone who is drooling over it borrow it for a while and it if works flawless with film being run through it and then developing it, there is your evidence. The only two certainties to the above issues I mentioned is actually using it. Don't be another one of those guys. I've bought cameras off them before that were promised to work fine, I get it and actually shoot with it and end up returning it or fighting with the person who sold it to me until something gets done. Not a fun way to spend your time.