A 12mm 2 barrel Pinfire with a trapdoor? swing-open action.
Stamped Courard Bte 162, with Belgian proofs ELG star in an oval and feint N.
You cock the hammers, pull the front lever and swing open the breech left-to-right to load.
295mm long with 148mm barrels. An unusual action for a pinfire.
I measured the length of the breech-block as 26.4mm.
It chambers the Eley London 12M brass case ammunition so anything under 26.5mm long.
Seems the length may have been chosen to a plan but some pinfires are longer length.