Research UL (Underwriters Laboratories) TL ratings to get real ratings on safes. A TL30x6 stops 99% of bad guys, but no safe or vault is 100%.
I have managed the installation of concrete and steel bank vaults in new construction scenarios. The specifications are normally provided by the bank. A designer admitted that no security system, short of lethal response to intrusion, is 100% secure. But he did say that anyone that "breaks into" the vault would leave enough evidence for investigators to capture the perps. It would take a lot of time and tools and sweat, not to mention other security systems that would have to be intricately disabled to give them that time.
Then he said something I had never considered. In all security endeavors, there is no defense against a clever heist (vs. "break-in"). In almost all cases where cash or box vaults are breached, it involves an employee (inside job). In these cases, knowledge is the weapon. And it's up to the bank to keep that knowledge secure. I thought that was insightful.