Is there anything you can look for to tell the condition a transmission is in if its not on the car?

Also how can you identify transmissions from different cars. There are numbers or codes correct? If so anyone have a link to tell the difference?

Also a 94 del sol si tranny= an ex tranny correct?

I havent really dealt with transmissions before but Im trying to get one to swap for my mini-me. Help is always appreciated.