Well, a pre-model 24 or 26 will have a 5- or 4-screw frame, and depending on the age of the model stamped gun it may be a 4- or 3-screw.

The model stamped examples of these two guns (as well as the 20, earlier 21 and 22, and 23) are pretty rare; collectors know this and values rise accordingly. As noted above the model 24, and 21/22 were reintroduced later.

__________________
Alan
SWCA LM 2023, SWHF 220