Stocks look correct for the eras the revolvers were made. Walnut concaves stocks are from the 1920s and the hard rubber stocks were available throughout production of the Safety revolver. 167012 shipped around 1903 and 251736 shipped maybe 1924. Guns were shipped out of serial number order so either one could have left the factory a year or so before or after. Only a factory letter will tell for sure.
You should make sure your friend knows that both those Safeties are considered as modern firearms by the BATF, so are subject to all regulations of both Federal and state laws.
Forgot to add that the proper name for the revolver is 38 Safety, 4th Model and 38 Safety, 5th Model respectively. The company also called them 38 New Departures.