These are some of the lamp brackets I have. Left to right they have these characteristics. Do you know what they are for? I think I do.
#1 Has a "D: cast mark. Square mounting holes.
#2 Cast in number "T7258" Round mounting holes
#3 Square mounting holes.
#4 Round mounting holes.
#5 Has Ford script. Sq. mounting holes.
#6 Square mounting holes.
I want to add that these are all old OS Ford T parts. They all came out of old Ford dealers. Some are rusty. I have more in other boxes. These came out of one box that I had not looked at for 25 years.