I tried to enlarge the photo some so that I could get a better look at it. Looking at the closure of the jacket I saw that it was a reverse image so I mirrored it to make it look the way it would if you were looking at the subject in person. Some observations:
The belt appears to be shifted so that the buckle is behind the sword quillon.
The scabbard is on his right side but there is something behind it that could be part of a pistol or something else.
On his left between his arm and sword blade is something that could be part of the back to his chair.
His sword guard appear to be thin and have a ferrule above it and below it. This thin-ness could be due to the guard being flat.
The knuckle bow does not appear to attach to the quillon the way a chain would and may be a flat, rigid piece of metal.
The blade appears to be blued and to have designs on it. It may have a single edge and flat spine rather than two edges.
The clam shell guard appear symmetrical. I could not find a match but it looks similar to French examples that have a shell or spider web motif.
An 1840's to 1850's militia officer's sword would be reasonable.
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