A great find!
The style is indeed the old "schuetzen" style as found in
Austria,
Germany and Switzerland.
The backsight is not just old, it is positively archaic, from the (flint) "stone age". I was just about to write that it could be a "drum & nipple" conversion of a flintlock when the above post appeared, and one look at the lockplate reveals that it is indeed a conversion. You can see that the flintlock pan casting has been cut out (and a ragged edge remains).
I have two such conversions, one done expertly and one by the village blacksmith, both acquired in my fruitless search for an original flintlock target rifle. Alas, just about every "serious rifleman's" flintlock was converted to percussion in the 19th century as the serious user wished to maintain its utility in the percussion era.
It is not a military rifle, but a predecessor of the type of private militia rifle that later became the
Swiss target rifle. Military rifles did not usually (although tempted, I'm avoiding the use of the word "never") have either set triggers or the deeply curved "schuetzen" buttplate. The fitting of a bayonet lug
may have been done for hunting guns in the 18th century, on a sort of "it might come in handy for finishing off wild boar" basis, as I have seen such fittings elsewhere, but I rather think it would have been the militia influence.
For identification and dating, that "bell-tower" backsight is possibly the most important feature. Even Viscount Bury's 1864 Manual of Rifling and Rifle Sights (which has some wierd and wonderful contraptions) has nothing quite like it. Looks like it needs a heavy dose of penetrating oil and then some careful adjustment.
So more photos of the backsight please!
BTW. The foresight button is more appropriate to a shotgun. I suspect that it is not original.