Looking further into my “box of brackets” I found one which I inscribed at the time I removed it from a 1967 Beetle decklid. In fact, it is written in marker and also scratched into the aluminum. This makes me know that I wanted to be certain to preserve its identity, even though I cannot recall the actual removal of the Bracket.
This Bracket affixes directly under the two outside studs of the license plate light housing. I suppose that all three of the stud nuts could be loosened sufficiently so that the Bracket could be inserted—all without complete removal of the housing—and the nuts tightened to secure the installation.
In the second photo, I note a potential weakness of this style of Bracket. The constant vibration of the plate, especially with the added weight, if there is a plate frame attached, may eventually fatigue the aluminum and it begins to crack at either end at the bend. Or…it could be that an owner kept bending the plate/Bracket to get the plate at the right angle or, perhaps, to keep the plate from vibrating against the decklid and destroying the paint.