I dont want to add a layer of confusion to the issue but consider both of these are Model 29-3's,
Both are blued 44 mags but with different frames and barrel lengths,
S&W also offered Model 29's and 629's with tapered barrels called "Mountain Guns"
The Model 29 is just a carbon steel N frame chambered in .44 magnum ,
The 629 is the same frame made in Stainless steel, barrel length, butt shape etc are sub options of the model,
S&W at one point attempted to bring order into the system by using a method of adding a "5" to existing blued guns , "6" to stainless versions and "4" to the airweight versions ,
Had they succeeded the Model 36 would have been the 536, the 60 would be the 636 and the 37 would be the 436,
The model 12 would be the 410, the 10 would be the 510 and the 64 would be the 610 but there were too many variations in existence that didnt fit the mold and it would have been a headache to go back and redo the whole system ,
To make matters worse they used new 4 digit model numbers on their next generation of semi autos instead of revisions,
beginning to see the conundrum?