1968 AC equipped confusion

Horizontal section = 1.5"
Site wouldn't allow me to post photo, said it was a security problem.

There feels like there is a shallow tab in the slot in the circle. The image is taken looking up.
IMG_20220813_190254153_HDR~2.jpg

The screw hole is .75" from the upper edge of the bracket. The tape is resting on the screw.
IMG_20220813_190517892.jpg