All 3 knives are versions of the 1219C2 USN/USMC Fighting/Utility knives.
During WW2, 4 companies made this knife - Camillus, Kabar, Robeson-ShurEdge and PAL.
Camillus made them during the Korean War.
Camillus, Utica and Conetta made them during the Viet Nam period.
Post Viet Nam contracts were filled by Camillus and Ontario.
Kabar did not make them from 1945 until the late 1970s when they started making them again as reproductions (no government contracts).
The following info is just my opinions and I readily admit I could be wrong.

But I don't THINK that I am.
The Utica, as a Viet Nam War vintage version, conforms to the final government specifications as of the end of WW2 with respect to construction, e.g., 1/4" thick, 3/4 through pinned pommel. The black sheath and black handle indicate that it was a later production knife (not early/mid 60s). Late 50s/early 60s sheaths were an "Oxblood Red" color. Occasionally, you run across a sheath that started out Oxblood and had the front dyed black to meet the new specs, but the back is still Oxblood.
The first Kabar is a WW2 version and appears to be a "transitional" piece, made at the end of the "generation 2" with a thick (3/8", peened pommel), but AFTER the specs had changed to put the stamps on the guard (which in this case is a straight, unbent version; later versions were slightly bent from the factories) rather than on the blade. The sheath is a non-WW2, non-Kabar aftermarket sheath that someone got to "fit the knife".
The last Kabar looks (IMO) to be one of the Kabar reproductions made in the late 70s or early 80s. The sheath on this one looks to be of the second WW2 style with the 9 staples, (first version had 9 rivets, later versions had 7 staples) but it too could be a reproduction sheath.