It's easy to be barking up the wrong tree with so little to go on here. Side plate shape is often a reflection of the lock plate, which suggests pre 1750, likely French - not to deny the possibility it could be much later - or an assembled piece.
The turn-off pistol was alive and well in the 1600s, same design as the one here. Basically the barrel being turn-off, the stock fore end shortened and no ramrod. The "Queen Anne" (1702-15) type, all metal but for the grip, with the barrel screwing on to the receiver which was integrated with the lock mechanism.
The Queen Anne was for the affluent, very labor/skill intensive, almost always silver mounted. The type in this thread only demanded the special skills in making the screw barrel and some are seen into late 1700s when the all metal box lock pocket turn-offs became popular - on into the perc period.
Internet search of turn off pistol or Queen Anne pistol will bring up a lot of hits.
Here are pix of some I have handled. The lower right, the earliest, I once owned. These are heavy pistols with bores .60+ cal, barrels 6-8" long.
This pix is a 'lock, stock & barrel' type of turnoff I had years ago, small, much more like the one in question in this thread. Germanic about 1730: