Name that hubcap

[Chateau Slate 66]

Back in the 70's, my dad had the auto shop at the High School build him a small utility trailer. I went with him to the junkyard to get an axle for it and on the way out, he saw these hubcaps. He liked them and bought them to put on the trailer. I have always wondered what they are off of. I thought maybe someone on here would remember them from the old days. The trailer also has its original bias ply tires as well.