I'm late to this topic, but own a pair of rolling Block target pistols. In 1871 Remington made significant changes to the frames that included the hump in the grip frame just above the grips, and also the concave curvature to the rear of the frame where it meets the grips. All models built after 1871 used these changes, which would mean everything else before this date was modified from the earlier style frame as your guns have.
Both of mine are based on the later frame style, and both custom modified by famed makers. One was done by H.M. Pope and is fitted with a Pope left hand twist .22 Short barrel. Hammer has been lightened, and trigger tuned, and a trigger stop added. The Pope barrel is threaded for a Maxim silencer for indoor matches, and has a protective collar when the silencer isn't used. I also own an original Maxim factory cutaway silencer for this handgun. I was told it was built in a group Pope did for the first US Olympics in St Louis in 1903.
The 2nd one was done by Pope's only apprentice, Arthur Hubalek of Brooklyn, NY and has a Hubalek Special barrel done to the same profile as original Remington barrels, and is chambered for .22LR. The action is also tuned and slicked up by Hubalek, and the grip frame is highly modified to be a full frame and two piece grips. Beautiful work by Hubalek and the larger grip feels wonderful.
The Pope is the top gun, and Hubalek is the lower gun.
Maxim cutaway for the Pope.
