Is this real or repro?

[CAGerringer]

I've got a '61 Springfield barrel with a Belgian proof mark on top, behind the sight. Anyone know what this might be?
Thanks,
Charlie Gerringer
Old Dominion Dragoons

[John Holland]

Charlie, after the Civil War many US muskets and carbines were shipped to France and used in the Franco-Prussian War. After that conflict many of the US arms ended up in the Belgian arms trade. Because of the proof house systems in place all of the arms had to be reproofed when they were sold by Belgium. Perhaps you have one of those barrels.