Thank you, Dietle, for the fine research on this important topic. You have accumulated a notable array of primary source information documenting and furthering our understanding.
A corroborating bit of information comes from the journals of John James Audubon. We know him best as the superb artist of birds. Additionally, to collect his specimens, he was also a proficient and prolific shooter of birds (a fact not often touted by members of the Audubon Society)! He traveled widely and knew guns very well. In 1821 while staying in New Orleans (then a commercial center of the world), he encountered his first percussion gun seeing it demonstrated by its owner. He mentions the owner putting a cap on the rifle and immersing the lock under water before discharging it. Certainly the percussion cap ignition system was in America in 1821 and was not yet in widespread use.
Thanks for sharing your excellent research.
Bill Paton