I was working on cleaning two kettles last weekend and thought I noticed a difference on the lower vent bowl holes. Only one hole on the first kettle had the slot for the tab on the daisy wheel and the second bowl holes had the slot on all three holes. one kettle is a pat pending and the other is, what i'm guessing to be a 72-73.
Ill have to look again and snap a few pics.
I am curious as to when this change happened and thought it might help date a kettle.