Take the risk of opening them all. If you've ever heard of counter strike global offensive, or CS:GO, first of all you've been living under a rock for 10 years, and second of all that's the whole point of cases. You either waste hundreds of dollars and make nothing in return, or waste hundreds of dollars and make more than that back or just get a dope looking knife. When push comes to shove, I'd open them. But that's just me.

Good luck