From what I can tell:
I have seen magazine ads for the H-B hatbox style vacuum from as late as 1966, and a newspaper ad for the "light look" style from 1963. I have seen the lite look model in both turquoise and yellow trim colors, I have only seen the hatbox with yellow trim. H-B closed their Racine WI plant (it was located at 1509 Rapids Drive - You can see it on Google Maps) in June 1968 and moved their production south to North Carolina, so I would guess that vacuum production stopped around then (they were booming with electric knife production).
Andy