No markings whatsoever on the barrel. Infact the C looks like it could have been caused by a slight hit from a punch or something. The barrel has 12 flutes.
I looked at my barrels again - I have 3 that are white, and 1 that is parkerized. 3 of them have "38-46-90 7" on them, and one has 355-355-89 on it. Also, two of them have made in turkey stickers on them. The machine marks, and shape of the 3-lugs on the parkerized one is slightly different than the others, but the others look exactly like yours.
Maybe someone sanded off the old numbers. They're some sort of part number or lot code because 3 of them are the same.
If you look at the thinner barrel portion, does it have tiny ridges down it where it was turned on a lathe? All 4 of mine do, and if not, someone likely sanded it down. I'm debating whether or not to thread mine to make them navy barrels, or just keep them in standard 3 lug.
One of these days when I get around to buying a 3 lug suppressor, I'll see if it fits the 3 lugs, and if not, I'll just thread them.