John, the lock is original, only the screws are modern replacements.
Please see another, almost identical arquebus with the same date and marks but without the flame decoration in my collection, and retaining all its original screws and long tiller trigger (the latter broken off on the sample in Nuremberg):
http://www.vikingsword.com/vb/showth...1539+nuremberg
I cannot remember ever seeing those rings of flames on small arquebus barrels.
Best,
Michael