Nice find there!! I have a Kenmore Whispertone I found last fall that's even earlier than this one, the Whispertone Dual Motor, which was their first offering in the early 90's for clean-air uprights. Take care of that, & in particular, order a new set of carbons for the motor....I believe these were still using Ametek motors. If you replace the carbons & take good care of it, these will last a VERY long time.
Rob