I also wonder about the Brazilian identification, though it is possible this is a mix-and-match gun that ended up with a Brazilian side plate. I looked closely at the right side photo and couldn't make out any Brazilian seal detail. The rest of the gun does not look overpolished to me, so if the seal was there but is now mostly missing, its removal was intentional.

Brazilians had the small S&W logo on the left side.

Check the serial number on butt, barrel flat, and rear of cylinder. Also on the vertical face of the yoke and underside of the ejector star, if you can read those without disassembling the revolver. They should all match, but may not. Brazilians can have parts that migrated in from some other revolver.

As you heard, the stocks are only 40 years old or so, and are not original.

The two guns for $400 was great buy. You did not lose money on this no matter how the final identification shakes out. We're just trying to get the right identity as an academic exercise at this point.

Can you tell us the serial number? (Or at least all but the last two digits -- x those out if you want to.)

There was a postwar Brazilian contract that, paradoxically, used earlier 1920s frames. Those had the large ejector rod knob. Possibly your gun is from the 1946 Brazilian contract. They were also marked with the Brazilian stamp that incorporated the 1937 date.

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David Wilson