Stainless!
Has been around longer than you think,Im 99% sure it was introduced by Thermador on built ins in the very early 50s, maybe even late 40s, GE and Hotpoint had it not too many years later, Our local furniture store has a top of the line double oven Hotpoint range from 55 that is Stainless, I have a 1955 Frigidaire french door oven and fold down cooking units that are stainless.