Tried some root word searches
I apologize for interfering in your discussion, but I love to search for the roots to words and I think I may have come to something that will tell you the origins of the mark.
I took the first of the inscription on this stock and came up with the word "maken" as a possible root word. When I put that into a search engine for European roots, since we knew the rifle came back from Europe bearing this mark, I came up with a Dutch term meaning "to mend" or "to repair."
It follows by logical extension that this stock may have been "repaired" or "mended" at some point in a Dutch or German facility, as the two languages share a common base for words in some instances. The location or repair facility's name in the top of the escutcheon is apparently long ago lost, but with a word like "repair" on this older stock, it seems pretty safe to assume that this item in some incarnation was "repaired" or "mended" in the Low Countries. These were good allies in the Cold War and would certainly have taken on repair of the many Garands left in their charge for their own defense.
Perhaps someone here knows of such a facility from their own time in that part of the world as a member of the services stationed in those parts or if, in fact, such repairs were commonly made.
As an aside from my own experience, I have seen the same oval cartouche on rebuilt Mausers surplussed into the US market in the early 1960's, although I never gave another thought to such a mark until I saw this one again the other day. It has been on my mind since I saw it and was unsure until I came across the word for "repair" or "mend" in searching tonight.
The aforementioned rifles were rebuilt in West Germany at the war's end or more likely in the 1950's as possible items to re-equip the new West German army.
I offer this as purest conjecture and for discussion as a possible answer for a long-asked question on this matter. We might also make inquiries on the Mouser boards for any similar marks they may be aware of in their rifles from the post-war era.:wave: