Winchester 1873 Carbine
That is a real strange barrel marking for a 73 Winchester. I have seen 73's with 66 barrels that are marked
HENRY'S Patent-Oct.1,1860.
KINGS PATENT-MARCH 29, 1866
These have been explained by someone having a barrel and changing it out. A front sight would have had to be added as the 66 carbine had the front sight as part of the front barrel, band.
Has your barrel got 5 or 6 Groove rifling? Is it round or octagon? What lenghth of barrel?
Serial # and Photo would help.
RK