This mystery is getting more bizarre....
I own a Eureka Upright 1425E which my parents bought for me in Florida in December of 1982. The box it came in (I kept that for many years after opening it), had the new Eureka lettering minus the curvy "E", along with the comic book characters you see in the commercial in 1978. The slogan on the box said "Gets the Dirt You Can't See". The unit itself, though, has the classic curvy "E" combined with "Eureka" in white on black - the old Eureka Williams graphic. This is on the hood as well as on the bag (like Swingette's wine coloured unit above). The bag has the white plastic throat inside at the bottom, and the handle is plastic.
It looks like Eureka was mixing things up as they transitioned over to the new "E"-less graphic. But as I said, the classic corporate signature was still there on a machine sold at the end of 1982, even though the box had the Eureka branding typeface.