My honest congratulations, man! You got a very, very rare and finely decorated Dutch matchlock musket, ca. 1600-20, probably for a guardsman of a town guard, possibly that of Amsterdam!
I collect only rather plain arsenal pieces but yours is a real beauty!
You are a very lucky guy, no doubt about that. Keep a good eye on your piece.
If you don't mind I would love to see more of it, and I am sure so would the rest of us. If it retains its original length it should measure about 160-162 cm overall, the barrel ca. 123-125 cm. Any marks?!
I attach scans of very similiar Dutch matchlock muskets preserved in the Livrustkammaren in Stockholm.
Have fun, you have deserved to be proud.