It's hard to say -
Many elements of the design are so perfect, they are still in use today. I do remember hearing and seeing one (in that order) in our high-school home-ec. classrooms and everything else in the room had been donated in 1970 - so maybe that is a clue.
Our teacher suggested these were especially good for fibrous materials, the pulsing preventing the fibers from tangling.
Congratulations - what a beauty!