Regarding J.P. Dannefelser, here is an excerpt from a letter of provenance that I did for the owner of a Mannlicher-Schoenauer:
"Mannlicher-Schoenauer 3651 was sent to J.P. Dannefelser which was a firearms store located at 19 Warren St. in New York City. J.P. Dannefelser was John P. Dannefelser, born in New York in August 1857. Initially a law clerk, Mr. Dannefelser was operating as a gunsmith by 1900. Copies of several documents referring to J.P. Dannefelser are enclosed. The store continued to do business until at least 1923 according to a check sent to the store by Annie Oakley."
I am not certain about where I got the reference to the Annie Oakley check but it was likely posted somewhere on the internet.