I think Hoppy Hopkins was one of the H's in H&H, and I can't remember the other. They were from MD., if I recall correctly.
I put one in my wife's flintlock, along with a small Siler, back in the early 80's, and she won a few matches with it at Friendship, competing against other women mostly shooting caplocks.
H&H was one of the first, that I know of, that offered round bottom rifling back then.
It's a fine barrel, but they haven't been made in quite a few years that I know of.
Jeff