Could have been, I have a '62 GT and it seems that each one has different custom option combinations. It may be a patch but it would appear to be at about the right height to be a light. The only way to be sure would be to remove the patch and see if there is a wire?? or remove the inner skin to look for same. A lot of work to maybe just find out it is a patch over a hole.
I guess you will find out for sure if you do a frame-off resto, or decide to re-insulate. Maybe someone has a good idea how to check this, barring an x-ray LOL.