[SDC]

Have you had the barrels out of the wood yet? The "Canons a Ruban" ("barrels of ribbons") marking is probably French, but the French would have definitely proofed the barrels on the bottoms of the chambers. If you tap the cross-wedge in the forward part of the wood out of alignment, then cock the hammers, you should be able to lift the muzzles up and disengage a hook at the chamber end, and separate the barrels from the frame.