And now a true gem....
This is the true definition of an error coin. The Mint made this denomination error. The client (TGBEX) had requested 20BTC but for some reason the Mint managed to make them as 25BTC. Dissatisfied with the coins, TGBEX requested the 20BTC to be remade but did not return the 25BTC coins, instead keeping them. They were never released to the general public. My understanding is that those coins may now be destroyed/beyond reach leaving this one as the only "living" example ...
The coin in the picture was gifted to me by Adrian of TGBEX as a thank you for the work I had done in selling the TGBEX coins