If possible, post a picture (or two) of the other side of the gun.

One of the interesting things about this gun is that it has a straight
tapered barrel, with no shoulder at the frame face. Only the model
of 1899, and the model of 1902 (no change) use this barrel. In about
1903, there was an engineering change that beefed up the frame
face, and the threaded portion of the barrel. This resulted in a
shoulder on the barrel, that exists to this day. That early engineering
change results in the guns being known as 1902 1st change.

Mike Priwer