Schmalkalden is somewhere near Suhl. I don't have a map before me, but it's in that region.
The Pistors were a very well-known and long-lived family of gunsmiths. I think they always worked in this general region. At one point, Thomas Wilhelm was working in Kassel.
The stock carving, indeed, all the decoration is very much high rococco, which takes the forms of the "rocailles" (shell like shapes), and "ruffles". Flowering vines are also commonly seen, particularly on South German guns. Baroque work consists more of the familiar "acanthus leaf" (in all its many forms), and is often a bit more symmetrical. Rococco thrives on asymmetry. Baroque also includes "putti", "the green man", bound captives, etc. Lots of "Ohr" ("auricular"/"ear") shapes, and "S" curves too. Baroque and Rococco blend in with one another, and often you find guns that don't have "pure" baroque nor "pure" rococco decoration.
This gun is about as pure Rococco as you can get...with the exception of the barrel decoration, which is very much an earlier baroque style. But, it seems, the barrel has been re-used, so there's that. I'd say the gun was from about 1750, more or less.