To my knowledge the Spectrum followed the Dimension 1000. Early Spectrum models had a Futura style power nozzle. Later more deluxe models had a headlight equipped Quadraflex Powermatic. The Deluxe ones have a gas pump handle with on/off switch on handle for brush roll and some models include variable speed and on/off switch for entire unit on handle.
Wish I could help further. I was about 10 years old, perhaps younger when Spectrums were on the market, I don't know much more about them. John Long has an entry level model with Futura style head. I was so confused when I saw it. Prior to seeing it, I thought that Spectrums only came with a Quadraflex. However his unit is completely original, factory specification!!!