Good luck! I've been collecting guns for more years than I care to remember. The filigree is usually sculptured to fit a specific shape, but I suspect they followed simple rules to create it because you instantly know when it is wrong. Well, instantly if you have wasted your life messing about with old guns

I have possibly the oldest surviving gun lock, dated mid to late 15th century by that nice Mr Pegler at the Royal Armouries. It's a snapping matchlock with both side button and trigger release. Amazingly after 500 years at the bottom of the Thames it still works and the engraving on the serpentine survives, it's a dragon.