Stophel,
It may be Dutch, but in my mind there are a lot of possibilities. I see the stock architecture as a pretty generic 17th century form rather than from any specific area. It's certainly architecture the French developed which spread to much of Europe. The lock design points to the first quarter of the 18th century as a likely construction date. The gun certainly isn't academic French work. The carving at the entry pipe is a spin off of French designs, but is a bit funky. I see all the posibilities you mention as well as it being a Germainic piece. I've tried to find connections based on the lock design, but haven't found anything definitive. One interesting feature is the squared out bend of the frizzen spring. I'm not certain how widespread this feature is, but I've seen it commonly on work from the Munich, Vienna area and into Czechoslavakia. I'd love to hear any thoughts others might have.
Thanks,
Jim