Jack,
At the time this was available, there were three lines of Hoover's on the market, A, B, and C. These lines individually would have consisted of a set of Convertibles, two DAM's and then the canisters. Some cleaners were shared between lines.
Depending on where you shopped, you could hit three different stores, and see three different lines of Hoovers.
The Bicentennial model was a promo cleaner. These were lower priced, less featured models designed solely to bring shoppers in. Not all the dealers had the promo models, just depended on where you shopped. I remember Tru-Valu hardware stores selling the bicentennial model for $59.95, and seeing it in a few Fingerhut type catalogs. You could buy the A-line U4061 Convertible for $65 or so, and it didn't have the headlight!
The interesting thing about it was the Bicentennial model was a two-speed, high performance model, identical mechanically to the A/B/C line machines save for one difference: the brush strips. It would have originally had the old style black strips, while the other models had the stiffer red ones.
Hope this helps!