Richard and Mete are right about analyzing being a positive method. But, if you have a clue as to what you have you might figure it out by some other means. Lets say you know you have some 51200, some 15n20 and some 1084. You could start you etching them. The 1095 would turn black and the 15n20 grey. The 52100 lightest. Sparks will tell to if you have a book that explains what to look for well. BUT, if you have some 1095 and some 1080 it would be very hard to tell the difference. same with 5160 and 51200. one stainless from another would be tough. Best to get a paint pen and mark them when you get them. but, that doesn't help now
I quess the first real question is now many different pieces do you have and do you know what types of steel you might have and maybe we help you tell on from the other..