Case Opening Plugin Idea

So I thought of this idea randomly last night and thought it'd be really cool to see it in a MyBB forum. It's basically like CS:GO's Case Opening. This plugin would have a Bronze, Silver, and a Diamond Case. To open those cases you'll need a key. What's the difference between the cases? Percentage of luck, and the items you receive. You can buy the Cases & Coins with either credits, or real money. Here below I created a quick visualization: