In over 40 years of digging, dealing, and learning about US Military belt plates/buckles, I've never seen that one. It appears to have the same version of mid-20th-Century-to-present "attachment point" that is seen on "souvenir/fantasy" belt buckles.
All of that being said... I don't believe I've seen everything there is to see. If I'm incorrect, let me know.
Thanks;
I also believe it is a reproduction. On the back there is one point that goes thru the holes in your belt to adjust the size. At the other end, the belt wraps around the large loop to attach the buckle to the other end of the belt..