Based on the guard style, butt profile [not too crescent], and nice sized capbox, your estimates appear about right. One detail seems out of place. The cast pewter inlay at the barrel wedge appears later based on being "attached" with two screws, both of which are brass and have what appear to be modern, flat bottomed machine-cut slots. If this observation is correct, the inlay must be more modern than the rest of the gun. Perhaps it was a later "clean-up" of badly worn/chipped wedge holes.
Shelby Gallien