This one you call a "bacamarte", as it came out from regional Portuguese smiths workshops; an assembly made with salvaged parts from weapons used during the French invasions (Peninsular war)..
The barrel has once belonged to an early Brown Bess musket, shortened to 44 cms. The lock might be a Portuguese copy of those equiping the 1756 Land service musket. The cock would be later, maybe a Portuguese original. The extremely short (ened) walnut stock is Portuguese. The butt plate in tongue shape, of XVIII century influence. The screw holding the barrel tang to the stock is in the inverted position, a system often seen in similar Portuguese pieces of the period. The belt hook has the so called fish tail shape. The royal mark on the lock is faded, as usualy in this "civilian" pieces, result of having been filed to prevent it being identified by Ordnance officials.
I hope (some of) you people like it; i do ... very much
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Fernando