Apparently, the Marines didn't do it that way, but the Army serial numbers had letter prefixes. RA was regular army, an enlistee. US was a draftee, NG National Guard, ER was enlisted reserve. I believe all officers had O and warrant officers had W regardless of where they came from.

The last four digits of the serial number with the initial of the last name was was sort of a code to identify property. Along with clothing, boots, etc., the soldier was issued a rubber stamp (e.g. G-2824) with which he marked his clothing, using permanent ink. This was not only a property ID but was also used as a laundry mark. Items of gear that couldn't be stamped were painted with the number, using a small paint brush. With unit property, such as helmet and helmet liner, the paint could be removed when the item was turned in. Rifles had a rack number, painted on the bottom of the pistol grip, which could also be removed if the rifle was turned into the depot for repair or if the unit was dissolved.

Jim

Jim