The shot I just uploaded is a D800 I found online where it's stated as if the D8xx is same build.
But to me it looks like the D810 is a plastic mount camera,,, the more I look at the images of your broken one Chris,,,
I can now see it's the self tapping screw-types used to mount the bayonet and the little contacts to make electrical contact between camera mount itself and electronics inside the camera,,, Just opened my own - I can't believe my eyes,,,,