Military surplus markings

[neo]

I have recently acquired a Military surplus 6.5L engine and am trying to determine how much I need to tear it down before use. At a very minimum, I plan on pulling the pan and a few mains to check the rotating assembly, pulling the valve covers and rotating to insure valvetrain all working as expected and finally, pumping up the oil pressure with my drill tool, then spinning it with a starter to get a (yes, cold) idea of the compression. Now, what I would love to do is to do it right, align bore, ballance rotating/reciprocating assy, deck and heads, etc. Unforutnately, not in the $$ card at the moment.
Here is my question: This engine has a bunch of white "X" marked all over it. I have searched high and low for what these mean, but can't find it. Anyone know? I know I have read about this someplace before, but can't rememebr and can't seem to find the info.
THe engine turns over fine with the expected effort. It is a 2001 506 block (Navistar double diamond) so it seems as though it will be worth the effort if not toasted. I am assuming (yes, i know the addage) it is pretty sound as other ones I have bought have not turned over as nicely as this one. Any insight on the markings is appreciated. Just have very low funds at the moment and can't put in what I would like and trying to figure out best approach. THanks as always.
Neo

[Dvldog8793]

Howdy
When I was active in USMC we marked JUNK with an X and good used with DRMO or sometimes just a D. Sometimes the junk was not junk but that's what we used the "x" for.