The stocks can't be original to the gun (the serial is at least two years too early for those), but the finish looks to be a very good candidate for original pre-war blue. As David says, the caliber is decisive. A .38 Special would make it a US police or other agency contract gun, a .38 S&W would be a pre-Victory BSR, although except for the mentioned Sourh African guns (which are marked), 4" barrels are very uncommon on those.

PS: We typed at the same time. So it is a BSR. Any other markings on the backstrap or elsewhere?