If you pre-ordered the special Collector's Edition of Sonic Mania (for any system, or the PC) this "Metallic Collectors Card" came inside your gigantic box of really great Sonic stuff.
However, it is made of REAL METAL. So, it's a great quality surprise. The silver-tone there is actual metal that has a glaze over it that holds the designs. It is different front/back. The card thing though, does NOT have the games code-key number on it, that is on a separate paper. This metal rectangle is just that: a collectible piece.