I suspect that they are zinc plated, mine are relatively rust free and I don't think cad plating would have held up as well for 69 years.
1957 Chevrolet 5700 LCF 283 SM420 2 speed rear, 1955 IH 300U T/A, 1978 Corvette 350 auto, 1978 Yamaha DT175, 1999 Harley Davidson Softail Fat Boy
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