Let me try to do something systematic about frame variations in the 1903 to early postwar I-frames.
They had adjustable sights or they didn't.
They had rebated frames or they didn't.
They had frame-mounted firing pins or they didn't.
Based on these three distinguishing features, we may observe:
Adjustable sight guns can be found with both types of firing pin and both types of grip frame. Fixed sight guns can be found with both types of grip frame, but only with hammer-mounted firing pins.
Non-rebated frames can be found with both fixed and adjustable sights. Rebated frames can also be found with both fixed and adjustable sights.
Frame-mounted firing pins are found with both types of grip frame, but do not appear on the same frame with fixed sights. Frame-mounted firing pins occur only in company with adjustable sights.
There are further correlations that can be distinguished based on barrel length, but that gets into the questions that OP raised on the top of this thread.
I'm not sure that saying all this was worth the electrons required to do so, because it is mostly intuitively obvious. But some days the OCD demons prod one a little more aggressively than they do on other days.
I'm having an out-of-beer experience right now, and may go solve that problem to take a break from the rigors of systematic description. Cheers, all.
