No problem, Mossdancer. I've been corrected on misinformation more times than I can remember. Until I ran across Mr. Trzska's article, I had a bunch of misconception about MK2s/1219C2s.
Unfortunately, sometimes, someone has some information and it gets published in a book or periodical. The information, as known at the time of publication is correct or at least not known to be wrong.
Unless someone runs across info down the road that is newer and more accurate, the incorrect info stays around. It's really hard to "unpublish" a very prolifically produced book, such as Coles' 1,2,3 or 4. Mr. Cole did the best he could with what was available to him at the time, but he didn't get it right every time.
One example of that is the infamous "V44" knives. He tagged the Collins #18 Pequeno Machete and its wartime authorized clones as the "V44"s, along with the Case fixed survival pack machete, which turns out to be the only real V44. But lots of folks still call them V44s.
And to answer your question, I have never seen a knife or sheath marked 1219C2 or 394831. If marked, the knives had USMC or USN-MK2 (or MARK 2). The leather sheaths have all been unmarked or stamped with a simple USN. The BM/VP fiberglass sheaths are all marked USN-MK2
The only reason the fiberglass sheaths have a MK1 or MK2 on them is because the Navy had the 2 models of knives. The initial specs did not include a branch of service indication requirement. The first Camillus versions with the split nut and the first thick pommel/round peen Kabars just had the manufacturers' names on them. I don't remember if the 1st shipment of Camillus thick pommel/round peened had a branch designation on them. Something else for me to research.