16th century and early 17th century pistols/muskets and rifles should have rounded screw tops holding parts together. Three of your screws have flat tops while all other looks 16th century.
The three screw tops could have been placed there as part of a restoration. I had a wheellock rifle dated 1604 restored, and it came back with a few flat screw tops as the gunsmith did not know that they should be round. I have yet to have this detail corrected.
All wheellocks in my collection has rounded screw tops. Except the few restored ones as aforementioned.
If anyone can find a photo of an original 16th century or early 17th century wheellock with flat screw tops, you will have proven me wrong
By doing a quick Google and Pinterest search, this little detail can be seen.