Before the model numbers and the dash sequence , how were factory changes identified.

They were not identified in the catalog or any correspondence I have seen. Guns were just called by their model names...Model 1902, Model 1905, .38 M&P square or round butt...and so forth. I seem to recall a prior discussion here that Roper began tracking changes internally...or maybe he inherited a previous methodology...for collector purposes.

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Guy
SWHF #474 SWCA LM#2629

Unless they were outwardly obvious, like the differently shaped hammer in 1948, mostly not at all.

That’s why we have all the collector-invented ex-post-facto terminology like the numbered changes, screw count, and such, which the factory and “ordinary” customers never used.

Changes have been identified in books about S&W firearms. There's a compilation of changes list in the Standard Catalog of Smith and Wesson 4th Ed., page 492 Appendix C.

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Jim
S&WCA #819

I usually check the serial number in the Standard catalog of S&W, it usually has the changes by serial number ETC M1905 change # 1, 2 , 3 ETC. Also the the Blue book of gun values I think.
SWCA 892