I tried to pick one of these at an outdoor antique swap meet once and after an hour I gave up. I went home and looked up just how the 4 sided mechanism works, and then realized it was not a wafer or pin tumbler lock in the traditional sense. I also didnt know which way to apply tension in order to unlock it, for all I know I could have been turning the wrong way for an hour, although I tried picking it in both directions.
take a look at this patent drawing..
http://i.imgur.com/wclIAT5.png you'll see some pivoting elements that the key presses up against and if your wavey key cuts match the depth of the internal pivoting pieces then they pivot as you insert the key and esentially unhook from the lock body so that the plug and key can turn. an even earlier patent for similar mechanism by same inventor:
http://i.imgur.com/nCqV5cJ.pngThe reason your ebay key isnt working is because it is probably cut to work in another Cleveland lock, and the wavy pattern on the key doesn't match the shape/size of the bits inside your lock.
good luck with your project!
Squelchtone