I'm not sure of the question. Are you asking what the King's Patent Improvement markings are? All 1866, 1873, and 1876 Winchesters had this marking on the barrel. Those reproductions sold by Cimarron have the marking, as they pay extra for it. Right now I am reading this off my Cimarron 44 W.C.F. carbine:
KING'S IMPROVEMENT PATENTED MARCH 29, 1866, OCTOBER 16, 1860- and at that point the printing runs into the rear dovetail and ladder sight, so I can't read the rest.
If your question was regarding what the King's Improvement entailed, it consisted of the wood forend and the side loading gate added to the Henry. Winchester even advertised the '66 as the "Improved Henry"
(The Texican Rangers CAS club have an 1-8-6-6 sweep occasionally and the starting line is "Who is this King fellow and what did he improve?"),