Drew is right. The different models are in "blocks" of ser. no. The ser. no. would put the gun into a model group. Also, on the bottom of the barrel lug, there is usually a letter stamped. It can be a T or a D, which tells us T for twist or D for Damascus. Unfortunately, I don't have a fluid steel Baker, so I don't know what letter they were stamped with. Then again, the ser. no. would again also help us. Some models of the Special(which were built in a ser. no.range)were fluid steel barrels.