Brophy and then Houchins' listed hammer guns as having two different styles of hammers, actually there are three. Type 1 was the high hammers seen on the Syracuse L.C. Smith's and used on early Fulton hammer guns until 1896. The highest serial number I have listed with this type of hammer is 53558. Type II hammers were slightly lower, ad stated so "not in the line of fire", these lasted until 1899, my records show 73456 as the latest. The third style or "C" started in 1899 and lasted to the end.
Yours from 1907 would be the "C" style. There were also four styles of locks but that is another story.