One will also see a different length screw in the two piece units. If I remember the later ones were shorter. Perhaps it saved a penny or made it easier to disassemble after the years.

Brian: The frame did not have a roll and pin. I just played and took the pin and roll from one of the orphaned Trojan frames and then wondered if it could be inserted into the D frame. It did fit. So Parker Bros did not put a simple pin into this 1901 D.

When absolutely everything is removed from a frame, what can be done with it? If it were a beautiful D frame, I suppose a guy could round up the innards and a set of barrels and some wood and bring it back to life or ... ???

I have dozens. From time to time, I sell off stripped frames as paperweights for $20 usually.
Some use them for engraving practice, or CCH trials. I have cut them apart to make jigs out of.
Putting a gun back together from one using misc parts, though it can be done, is a daunting task for most.