Appearing only two months after the Series 1 coins, Series 2 was a significant innovation. This new version utilizes a hologram with a small window to prove the presence of the first-bits and private key inside, making it impossible to rub the first-bits off and fraudulently print a new public key onto the hologram. It is worth taking note that these coins are in fact much more rare then the Series 1 1 BTC ‘Error Coin’.
*Numbers refer to series 2 1 BTC 2011 coins funded in 2011. There may be a small additional number that were funded in 2012 and are counted in the series 2 1 BTC 2012 numbers.