Marble's were not an official USN issue. Issue was the KaBar MKI, marked "USN" near the guard on one side, and KA-BAR/ Olean,N.Y. on the other. I don't know how common it was for sailors to replace the leather washers with plex, but that is what my dad did in WWII. He did his up in red and clear and it was really the only thing that I wanted of his that I cherished as an inheritance. He passed, and my mom kept it in a drawer in the kitchen for butchering deer. Somewhere along the line it was stolen. We know who it was, but I wasn't informed until it was too late, and Florida is a bit of a drive for me. Otherwise I would have no problem "persuading" the *** to hand it over.
(Side note: Dad joined the Navy on Dec. 10, 1941, 3 days after Pearl, at the age of 17. Coincidentally, it was the same day of enlistment for me, Dec. 10 [1969]. After boot camp he was an anti-aircraft gunnery instructor because of his skill with small arms and the ability to teach how to lead a target. He was thereafter billeted to the recommissioned U.S.S. Chenango, an escort carrier converted from a transport/cargo vessel, whereupon the ship sailed through the Panama Canal to the South Pacific. As tail-gunner in a Dauntless [Basically flying coffins for the rear gunner... you couldn't get out of the things if you went down.], he was wounded and afterwards was assigned to aircraft maintenance. After the war he put his skills to use working at ConVair in San Diego as an aircraft machinist.)
Anyway, I loved that knife so much that I hunted for years to find another MKI. Finally found one at a LGS (while dad was still alive) and was able to get it, with sheath, for $20. This knife, too, has seen it's share of deer. Takes and holds a great edge and is still in use to this day.
Sorry for the poor pics. My camera sucks!