For wire radiator clamps. Called "Corbin" clamps if I remember right.
You remember right, and isn't that always a great comfort?
Common, if I recall correctly, on Chevrolets and other General Motors products. A bear to remove with conventional pliers, unless you could come at them from the side. The best version of pliers for Corbin clamps had a rotating disk with the groove in it on each jaw, so you could orient the pliers as needed for tricky spots - yes, even back in the 1950s, auto manufacturers put components that would need regular maintenance in impossible spots in the engine compartment.
