The revolver may be a copy of the S&W Hand Ejector Model of 1926, due to the barrel marking. It appears to have a larger bore than .38 and is likely a .44 Russian or .44 Special. However, the cylinder doesn't doesn't appear large enough for .44's. The poster needs to measure the chambers and bore to confirm which it is.

I'm going to take a guess that the "B.G" in the oval is for Benito Guisasola, a known maker of better class revolvers copied from S&W.

The proof marks are interesting in that the the Lion pistol proof should not have been used after 12/14/29, and the "crown over shield with X" admission-to-proof mark should have been used after 12/14/29. Maybe the gun dates from around the changeover.

Obviously, an gunsmith needs to evaluate condition and determine caliber before you shoot it, if you intend to do so.

Buck