My .350 Rigby is #4981 and I am pretty sure it was built in 1924. I will have to check my paperwork on it to be sure.
I would guess that this one is certainly within a year or so of mine.
The "American style" seems to have evolved with advent of common scope usage. Makes sense here in the western US where hunting ranges tend to be farther. Longer ranges, more scope usage and therefore rifles with generally higher butts more inline with the barrel.
IMO, the Winchester model 54 and the prewar model 70s were the last properly dimensioned American boltguns. They feel very good as open sighted rifles. Not as good as my British guns though...