That looks like a 6 1/2" barrel, measured from the front face of the
cylinder to the end of the muzzle ?
Its a relatively scarce gun; they only made about 12,000 to 13,000 of
them, before making the barrel and frame nose heavier, and adding
the shoulder to the barrel.
The finish on these early guns is very delicate, so don't scrub too
hard. If possible, use burlap instead of 0000 steel wool, and soak the
burlap well in some kind of oil, like 3 in 1 oil, or Corrosion-X .
Mike Priwer