Charles Patton's post rang a bell:   At the New York World's Fair, 
1939-1940, I recall seeing discs of aluminum (several inches in diameter)
levitated several inches above an AC powered magnet.  

It seems to me I recall seeing this described in popular science magazines
of the 1950s as well.

A long time ago, and memory is fallible, but I think it is correct.

warren

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