"Parlor pistols" used a number of actions (including auxiliary barrels for guns like the Luger), so I don't think the action precludes it being in that category. Still, I don't think it is; with the short barrel, large caliber (judging from the extractor) and rudimentary sights, I think it is a pocket pistol from around 1865-1875.
If Heeveltje could provide some pictures of the barrel or some measurements, we might at least determine the caliber.
Jim
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