I can only speak top the B&M's USRA DS cars.
I have the builder's photo from 1919 -- no fascia.
I have a photo with a 1934 reweigh date and pretty fresh paint. It has a fascia board. Tempting to assume it has been re-roofed, but it's still Murphy.
I have two 1946-47 photos, both with the fascia boards, still with Murphy roofs. Both have the Minutemen herald (rolled out in the summer of 1946), AB brakes, and Ajax hand brakes.
In between the last two photos, ca. 1939-40, the reporting mark would have changed (from B&M to BM).
So, with the B&M cars, the very best that that a single RTR model could do would be to accurately represent maybe a decade (or less). Unfortunately the Rapido model doesn't seem to represent any particular reality. It lacks the fascia board, and has a stemwinder in conjunction with AB brakes. The paint scheme is1946+, but the original 500 cars were down to 24 cars by 1950, and 4 by 1954. So the Rapido car might be useful as a fleet builder, if one is not too fussy about prototypical accuracy, and if you model ca.1946-49.
This is why I don't too excited when new releases of RTR cars are announced. YMMV of course.
Swall Meadows, CA