These bars were created from 100 BTC bars that were not funded or sold. In order for Mr. Caldwell to confidently sell unfunded bars that were stamped with ‘100 BTC’, he came up with the idea to add a laser-engraved ‘ZERO BTC’ directly onto the hologram to make it clear that the intact hologram was not interpreted to mean that the bars contained 100 BTC. Only four 2FA 100 BTC bars were made, none of which were funded at the time of purchase. In addition to the ‘ZERO BTC’ engraving, ‘2factor’ is also engraved onto the upper half of the hologram. These four bars are some of the rarest Casascius Bitcoin-denominated items with the exception of the unique Prototype 1,000 BTC Gold Coin, two 500 BTC Bars, and unique
1,000 BTC 2FA Unfunded Bar.