Regarding the letter followed by 2 or three numbers, I have speculated that it might be the identification of an armourer. I have only seen the letters on the low side of the alphabet, and the numbers never seem to go higher than a couple hundred. Perhaps the letter represents the armourer/inspector, and the number represents a sequential rebuild or refinish, or maybe the work order number?

A weapons tech who I used to work with was at 202 depot prior to coming to shilo. He was in a section of a half dozen that would rebuild .303s. Apparently the civilians made it a point to drag out the rebuilds to only a couple a day. When the 4 civilians went on strike at one point, the remaining two military corporals doubled the daily production of the section.
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