I've used one of these on my earliest record player machine, and heard "The Walrus Was Paul', on a 7" Berliner record from 1850. The best part of the Double-Acting Reproducer is that one can play a record both forward, and backward simultaneously -- allowing the listener to experience nuances not possible with ordinary sound-machine "heads".
Sorry, I know it's bit late for April Fools Day, but I just couldn't help myself.
-Franeola