The 11-digit numbering system was officially introduced July 7, 1952, and was gradually implemented, and widely in use by early 1953, which makes it a little late for the first years of the Korean War. All items received the FSN prefix (Federal Stock Number) followed by 11 digits, 3139-121-6210). This system was in use until 1974. It was then replaced by a new system preceded by NSN (National Stock Number) followed by 13 digits, 3139-00-121-6210).
For Korea I would opt for either the standard WWII numbering (7 digits in a single group, i.e. 9777300) or the 1947 numbering (7 digits in 3 groups, i.e. 9-221-200) simply designated Item No. (no prefix).