Tim Trager described the original 1920s Flex-a-Tone in 990822 MMD.  New
versions (of unknown quality) are sold by LP Music Group, Garfield, New
Jersey, which specializes in Latin percussion instruments.  They say:

  "The LP Flex-A-Tone is a unique instrument that creates a wave of
   eerie, saw blade-like sounds though varied pitches.  Bend the spring
   steel with thumb pressure as the wooden balls strike the surface.
   With a little practice, any song can be played on the LP Flex-A-Tone
   -- we've even heard the Star Spangled Banner played on it!"

Visit the LP Music web page and see the photos:

http://www.lpmusic.com/Product_Showcase/Sound_Effects/lp_flex_a_tone.html

Another site with a nice photo is  http://www.watsonsauction.com/282.jpg

Robbie Rhodes