Well that's the way to go about gun collecting. Not making fun of you but acknowledging that I do it that way, sometimes. Sometimes I get a set of dies in trade or once I got 50 pieces of brass. Oh yeah, I understand.
I guess the Police Positive Special would be what you're looking for. IIRC there are 2, 4, 5, and 6 inch barrels. Time frames, not so sure of that.