I don't have any real input on the subject of E.M. Reilly and co as gunmakers. I do have an interesting and useless little snippit of trivia for you though.

Reilly took over the premises of 2 rue scribe in Paris. The person who leased or rented the same address immediately previously to Reilly was an American man by the name of Adam Worth. Worth was a man of high intellect and intelligence, and he was also a master criminal wanted on both sides of the Atlantic.

This man Worth, was the person that Arthur Conan Doyle based "The Napoleon of crime" aka "Professor Moriarty" on in his Sherlock Holmes stories. It is believed Worth used the premises as a casino and front for his crimes.

Told you it was trivia, but there you go.