This is the 'Celebrating the Life of Stephen Hawking 2019 UK 50p Brilliant Uncirculated Coin' available from The Royal Mint. The coin features a stylized black hole on the front, along with the equation Hawking developed that explains black hole entropy (which he also requested appear on his tombstone, and does). The reverse, like so many other coins around the world, features Queen Elizabeth II's face. Unfortunately for those looking to spend some Hawkings, the coins are commemorative and, despite their 50-pence face value (~$0.66), cost £10 (~$13.25) apiece. You'd be foolish to spend that on some candy in a checkout line. Personally, I just bought one and plan on using it as my new lucky lotto scratching coin, which is particularly fitting considering the lotto is just a giant f***ing black hole anyways.
*dumping pile of losers in the trash* Some retirement plan this has turned out to be.
Thanks to Joseph A, who agrees everybody needs a lucky coin.