Join Date: Dec 2014
Location: Black Forest, Germany
The monogram of archbishop Johann Philipp von Walderdorff is undoutablyJPC = Johann Philipp Comes. My mistake, I overlooked the meaning of the "L" on the barrel of your gun.
The monogram on your flintlockgun "JPL" must belong to another owner. The only possible solution for this JPL is Johann Philipp Graf von Lamberg, bishop of the bishopric of Passau in Bavaria between 1689 and 1712. This means that your gun must be much older than said before. The maker thus must have been Georg Daniel Spangenberg, who was born in 1670 and died in 1752.
Sorry for the irritation