So the 1949 film The Third Man is to blame for the proliferation of all those Zithers in schools all over the nation. I don't believe there was one classroom anywhere in the United States in the 1970s that didn't have at least one vintage Zither sitting on a shelf. Where are all those millions of Zithers today? Sitting in landfills leeching toxic chemicals in our ground water? Precariously stacked 15 feet high in a forgotten storage closet in some elementary school, waiting to tumble down accompanied by tragic yet hilarious noises on the vulnerable and unsuspecting heads of curious children exploring the auditorium? Shipped to puzzled children of developing nations as critical teaching supplies? Cool tune, though.
The Zither is a fine example of vintage Trend Ort.
As partial evidence that there was a Zither craze that swept the nation once upon a time here is a comic book advertisement from Love Letters #10 (1951).