Although struck over twenty five years ago, this new discovery was just certified at PCGS. It is the only known certified two headed or two tailed coin that is also a die cap. The odds of this combination occurring are extremely rare.
There are approximately thirty genuine two-headed or two-tailed coins that have been authenticated by ANACS, PCGS and NGC. There are only four known "Two Tailed" U.S. coins: three Quarters and one Dime. One of the Quarters recently sold for $80,000.
I have handled most of the world coins that were struck with either two obverse or two reverse dies. Two of these are Canadian Copper Cents that were struck with two reverse dies and authenticated by PCGS. I purchased these in a Canadian Mint Error Collection and they have since been featured in a front page Coin World article.