If they were QTR window pivots they'd have a hole in the ball...I was thinking maybe the parts of some 60/70s cars front or rear 1/4 window mechanism or sun visor bracket
They might make a good paper weight if you don't have a use for them.All good answers so far. I'll add another possibility- a small cleat you could slip a loop over to hold...?
I was thinking the fixed bracket part that the rotating arm would get the cup clipped over.If they were QTR window pivots they'd have a hole in the ball...