USGI M1 Carbine cartouches

I just bought a USGI surplus Stock from keep shooting for 42.77 shipped. Its a little beat up like the description said, a little bit of the toe is missing as it was banged off by something and the buttplate shows a small dent in it where it was hit, but other than that it is perfectly fine. Anyways onto these cartouches that are on it. I know the P is an inspection stamp, however it isn't centered. I also Know it is a Robert W. Irwin replacement as well. But here are the rest of the pictures. I have no clue What The White D 3 is for.

Most likely being where it is that it's a rack number in an armory on a base somewhere. The P is for a rebuild proofing.