That's interesting, i can't tell from those pics if it is original or a reproduction. One thing I wonder about is that the trunnions are placed very far back so I think the tube would be muzzle-heavy, which means it is someone's not-too-accurate reproduction.
I can't see any cascabel on the breech-what's the breech look like?
All military tubes of that era and later had many markings, look for those, if none, you should worry. Look down bore with good maglight on 'spot' focus-most reproductions can be detected by looking down the bore as that is the place repro-makers don't worry about too much.
If it is an origiinal military tube from any country's army, it would be worth probably at least a few thousand dollars here in the US, and probably more.