Flat metal piece
the flat metal piece (I am calling it a hasp) seems to be my problem. flat metal works for cabinet backs and coin doors. It slides against the rest of the cabinet and holds the lock in place.
This machine has a "security catch" attached to the coin box that sticks up perpendicular to the hasp. Turning the hasp would push the coin box out the front of the cabinet. Unless the hasp had a notch cut in it to grab the security catch and hold it in place.