there are/were a couple of manufacturers
(past/present) which fulfilled knife contracts for the u.s. government.
all such us government issued (usgi)
knives will bear a stamped "U.S." mark.
and much like Ka-bar (union cutlery then) ,camillus was a pioneering ww2 contractor for the USMC and USN mk 2 knife.
after the war this knife pattern was
no longer exclusively USMC or USN service issue
its a mouthful of a name
Knife, Combat, Sheathed Specification MIL-K-20277
however "kbar/k-bar" (note spelling) is the accepted generic term to describe this knife pattern no matter the stamping marks present.
however many tend to mix up kbar/k-bar
the generic term with "ka-bar" the brand name. so its probably safer to call em "marine combat knife"
but current ka-bar is termed as the f/u (fighting utility) knife.. though many would readily describe them as the "ka-bar usmc knife".
hopefull the real experts who specialize in the known (and at times obscure ) history of this knife pattern would turn up here someday to fill in the blanks...