In Golden Age you will find many awesome features such as mystery boxes that generate random rewards AND mystery wheels.
HOW DO THEY WORK:
Each wheel has defined and planned rewards that can be achieved. Some have great probability while others do not (this is also how a mystery box works!)
When you click on a wheel, it picks a smaller number of it's SPECIFC reward list and let's you spin from them!
In a visual manner, this is how it works:
The key is every-time the wheel is opened form your bag, it rolls from what master items you can get! This is why everytime a wheel is opened, new prizes can appear!