Just my 2 pounds

At UK, they have 2 pounds in the form of coin and it comes to my surprise that their 2 pounds is so unique ! It's silver in the middle but gold at the edge of the coin. The "main page"(probably too much into computers stuff) or simply the face of the coin is the image of Queen Elizabeth II and it's written on the coin's edge "ELIZABETH II DEI GRA REG FID DEF". I need someone to decode it ! What's that mean !?

The back of the coin is printed with symbols and I need a decoder as well. Probably those symbols do really mean something. Da Vinci Code ? Ok, I had gone too far.

System.exit(1);