Here is the 1971 quarter dollar in place. You can see how, with one screw, it could be tilted across to sit under the tail of the strat trem to stop it moving back.
One of the great things I enjoyed the most about building the EVH guitar was all the interesting little bits of information and history I picked up on the way
Click image for larger version. 

Name:	EVH body.jpg 
Views:	213 
Size:	124.3 KB 
ID:	41506