I've never been in an arsenal, but I HAVE been in canning facilities. It's a lot easier to run an empty can through a production line where the contents are painted on the can, than to run a 20 lb can full of ammo through the same line. My guess is that the cans are pre-painted when a lot is scheduled for production; that way, there is no need to mark them once they have been filled & sealed. Cans where the lip is damaged won't seal, so they will repack these using a pile of spare cans, left over from various lots. It appears that they use stencils & small cans of paint to apply the correct lot number. Since stencils are hand cut, that would likely explain the "LS" mistake.