Camillus made the black leather handled version from 1964 to 1984, so there was a 2 year overlap of Camillus and Ontario making them.
If he was issued a "KABAR" brand Kabar during the VN war, then he was issued a holdover in the stock system from WW2 as Kabar did not make any 1219C2/USN-MK2s from 1945 to 1975.
If it was black handled, then it had a "makeover" before being issued - the Marines changed the specs to black in 1963.
On-hand pre-1963 leather goods were dyed black upon issue so as to meet specs. Items already issued were also dyed black to meet specs. Both types (NIS and issued) of items have been found to have been dyed on both sides and also just on the face, with the back side being left brown.
Kabar first made a commemorative in 1976 and it sold so well, Kabar ramped up production for the model 1217 and have made them and the various versions ever since, with brown leather handles like the originals or the kraton handled versions (starting in the late 1997 with the 1245).
