I just got a D-33 off eBay. It’s the model after Monica and I’ll call her Queenie, I’m not feeling too creative at the moment with regard to names, lol. Queenie and Monica look as alike as two sisters can: Queenie’s top ornamental grille and powerhead cover look to be the same moldings but are chrome instead of brown and she has the automatic cord reel in the base. I really wanted the latter but it probably contributes to her 25 pound weight, she outweighs my Kirby Legend II by five pounds and that is no lightweight! In comparison a two-speed Tristar CXL/Compact C-80-2 is a svelte 15 pounds even though it uses the same Lamb motor as the Filter Queen.
The literature that came with mine is dated February of ‘82 so I figure it was made sometime after then. Once FQ got into those earthy browns they stayed with them forever so I’d guess Monica was made well into the ‘70s.
For some years Health-Mor (Chicago based manufacturer of Filter Queen) offered a BOL vac called the Princess. It’s basically the same as the FQ but grey in color with less chrome and a one-speed motor (some earlier FQs also had this). The Princess was sold through vacuum cleaner stores unlike the FQ, I’m not sure if the door to door FQ salesmen also sold Princess. The Princess name was additionally used on a re-badged German made upright for awhile but I think those are pretty rare while the basic FQ Princess is not. Just like Kirby and Compact/Tristar, Health-Mor made a very functional and high quality product intended to be maintained rather than thrown away after a couple of years.