That's a nice looking '80 blue. Must have had an overrun of "B" stamp vents or a "late '80" since 1980 was the last MBH year.
At any rate, its super sharp! I've been thinking about your red since you first shared it, it has the specs of what I'm thinking is a 1975 kettle. Maybe late '74 at the oldest... I'm thinking that if Weber's fiscal/model year begins in October, then they must begin switching to the following model years specs but not w/o using up previous parts..... which would account for overlap in certain kettles vent tabs, ash pans, wheel styles etc.