There are stamps and markings all over the frame of most S&W revolvers. For instance, I took the grips off my 642 that I am carrying right now. These stamps appearon the grip frame: B15. "K" in a circle. F3U. "J" in a triangle. 943XK. 21104 143. On the cylinder: E. On the crane E 143. To the best of my knowledge, they are assemply numbers, to make sure the parts stay together during assembly and finishing and inspector marks.

The "K" in a circle can't define the frame, since its a J frame. The "J" in a triangle may designate a J frame. The B15 can't designate that its a Blue model 15, since its a stainless and aluminum 642. So, I think most have no real utility for a collector.

Some may designate the material the part is made of before finishing and some designate a final finish IE blue or nickel. Or a refinish or trip back to the factory for work.

I hope I got all that right...