Knife with "Thekenbeschlag"

[Martin Moser]

And that's as per the finds is it? Odd, you'd think it'd make more sense to put the rivets through the back part of the plate.

Yes, the fitting has no rivet holes on the back side, or in other words, the rivet holes on the front are situated so that they miss the semicircular narrow plate of the backside. There may of course have been a separate backplate, but since the fitting only has been found we can only speculate on this.