03A3 "I" Cartouche?

Is this a cartouche, and if so, what does it denote? I took off her repro sling tonight to replace with an original 1907, and I saw this mark for the first time, it has escaped me all these years. The stock is really nice and the mark is really crisp, so I assume it's a cartouche and not a dent. I did a google search and could find nothing on this mark, so it's time to ask the experts. Thanks guys.

The rifle is a June 1943 Remington. The stock is pinned, with a "no box" FJA, crossed cannons, circle P.

https://www.milsurps.com/images/impo...cc912a8e-1.jpg
https://www.milsurps.com/images/impo...e9e7bfe6-1.jpg

Probably a subinspection stamp of some sort. There is little or no information out there on them.