Shop-Vac
Probably late 60s,early 70s.Shop type vacs entered the household market in the 60s led by Delta and Craftsman dust collectors for the home workshop.The 'flat top' is dry pickup only.The wet pickup motor was raised.Before these it was typical for the old house vac to be moved to garage and basesment when a replacement was bought.Yours is somewhat plain next to later cans that were almost pop art such as my red/white/blue Penncrest bicentennial that I actualy found on the 4th of July.