Coldsteel - thanks for the update on condition, etc. Dan is coredt, in that the grooves at the muzzle may already have some filing done, kind of a flaring, to allow loading a patched ball.
: With sights marked to 1000 yards, it MUST be for a short conical as a round ball that size will not travel 1,000 yards. I believe somewhere around 700 to 750 yards is the farthest a round ball will travel, if under .80. A .60 calibre round ball, launched at 35 degrees is supposed to have a maximum range of 600+ yards. I'll have to check this out on my ballistics program once I get home next week.
: In 10 bore, 72" twist is not unreasonable for a short conical bullet. Note that a conical twist in Britan was 72" & 78" in a .58 cal., ie: 500gr. conical, which was about 1-1/2 calibres long. Seyfried's (large)12 bore single with fully rifled barrel came with both round ball and conical moulds yet had a twist slower than 100". The Conical mould cast a bullet just over calibre long, but weighed over 800gr., similar to an 8 bore round ball.
: I might be wrong, but sighting to 1,000 yards certainly would be foolish on a round ball gun.