First of all... I'm too stupid to find the edit button. Sorry guys.
Second, I found an alternative to the Brown Bess.

Attachment 84638Attachment 84639Attachment 84640Attachment 84637Attachment 84641

- Flintlock Pistol -
Overall length: 38 cm / 14,9 inch
Barrel length: 20,5 cm / 8 inch
Caliber: 15 mm / 0.591"

The lock marking is a lion stamp and a crown with the number three.
So, after I googled a few hours (mostly wrong), I found out, that this shoul be a british gun from the 19th century.

Opinions? And please don't say its fake...