Congratulations on your Hoover purchase. I wonder about it being a Model B others' models are typically 4-digit #s. In the last 30-35 years the model ids have letter prefixes (U for uprights; FA for floor machines, etc.)
Here is a partial list of model id codes and names for the various floor scrubbers/polishers/shampooers:
1940s: Models 0210s/Polisher (& Rug Cleaner)
1959-66: Model 3500s/Floor Washer (& Rug Cleaner w/Pick Up)
1962- ? : Models 5000s, 5100s/Polisher (& Rug Cleaner--"Mickey Mouse-style")
1962- ? : Models 5300s Shampooer ("Mickey Mouse-style")
1962- ? : Models 5400s/Shampoo-Polisher ("Mickey Mouse-style")
1980s: Model F2000s/Floor Polisher (& Rug Cleaner)
1980s: Model F4200s/Shampoo-Polisher
1980s: Model F4300s/FloorMAX Supreme
1967-1987: Model 3600s & F5000s/Floor-A-Matic (Scrubber & Shampooer w/Pick-up)
1987-2001: Scrub 'n' Vac (Scrubber & Shampooer w/Pick-up)
1994-1999: Models C3800s/SteamVac
1999- : Model F6000s/SteamVac WidePath
1999 - : Models C5000s/Commercial Single Brush
2001- : Models FA300s, H3000s, FH40000s/FloorMATE SpinScrub & FloorMATE Deluxe
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I happened to find an ad that looks like yours (claimed to be from 1957 although I didn't see it anywhere on the ad itself)--Hoover vacuum cleaners out during that era also colored in "Heather Rose Pink" were: Model 85/Constellation (1956-57) and Model 65/Convertible (1957-59):
