found it on ebay, i don't know if it's rare or not though.
http://cgi.ebay.com/C-ONE-CRANK-PULLEY-CEL...=item2562690be2

I dunno, not saying its not true, but if I was COne, I would put a stamp on it or something, so everyone knew who made it.

they don't do it because it would affect the pulley's balance.

I was thinking about that after I put that up there and looked up some cone stuff. It does look like a c one pulley. Two things (off topic a bit), one, perhaps a sticker then. Two, if you go through all the testing and whatnot to ensure the pulley is good, Im sure that some engineer can figure out a way to put a stamp without affecting weight/balance.