That "backing plate" is what the magnet rubs on, doesn't appear to be working...no ware.
Should have three hardened allen or torx, countersunk machine bolts holding the plate on.
May need heat, I did when I did our 63.
The studs can be punched thru from the outside.
"Sticks & stones can break your bones...and hail will dent your Airstream"
So when is this..."old enough to know better" supposed to kick in?