I believe that hammer (mening the steel or frizzen) was the common name both sides of the pond. Even in percussion arms, the "hammer" was still called the cock.
It's just us with out modern terms that hav ealtered it.

All hammers (frizzens) must have a very hard face to work, and the muskets were fitted with these as standard. Not sure why in the OP Gage sounds innovative, when they were always that way.
I'm a bit non-plussed on that one!

Best,
Richard.