Hey Chase
I dont know how I missed this one, Its from the early 70's im guessing,only because of the metal base. Its sister is the Kenmore Twin-fan. Im thinking they went to all plastic around 74-75 mabe before Hoover even. My grandmothers Neighbor had an all plastic she gave me with the maual and paperwork and she got it in 74 or 76. It was a BOL model but she also purchased the attachments for it.It was in bad shape tho, the vinyl bag was sewn many times at the bottom and held together with safety pins. My cousins mother also gave me a 2speed Singer around 89 with cord rewind and she said it was about 10 years old . Hope this helps a bit.
Also did you check the underside nearest the hight ajustment pedal sometimes they would stamp the date there on the plastic ones.
Kenny