Vent window...so you can get some air without rain or snow.
A governor....you could set it to any speed...and it would buzz if you hit that.
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My parents had that feature on their 1962 Buick. Us kids would sneak that to buzz at 40 mph. To annoy Mom. Certainly knew better than to do that to Dad.
Never saw that feature again on any car. Until now. My 2021 Volkswagen has that as standard equipment. I set it to alert me when I hit 75.