Mannlicher Mauser markings question

[DavidJayUden]

Here are a few. Please disregard the tape around the forearm: A temp. fix while the AccraGlass is setting up.
Again, my question is what is the cartouche and numbers on the stock doing on a sporting rifle, which I assume is a sporting stock, not a converted military stock. And also there seems to have been a plate just below the C 216, as evidenced by the 4 posts in the rectangle that have been cut or removed.