As I mentioned, those guns were made at the arsenal in Maubeuge, a city in Northern France about 50 miles south of Brussels, Belgium. The "Imp" would stand for "Imperial", which means the lockplates were made or engraved (re-engraved?) after 1804, when Napoleon became emperor. The change could have been made in 1811, which looks to be the date stamped on the stock and may indicate the date of the conversion.
Jim
|