They even did a video about it:
These dragon coins bear the likenesses of Jaehaerys I Targaryen (the Old King), the pretender Daemon I Blackfyre, and Joffrey I Baratheon.
(No, silly, they're not made of real gold. If they were, they would be considerably more expensive. They look good, though; bright and shiny with a nice heft to them. And if there is enough demand, Shire Post Mint might even do a short run in real gold for collectors willing to pay the price.)