I remember in junior high how they were always telling us that Dudley-brand locks were preferable over Master-brand locks.
I think I found that locks (though I don't remember what brand, though I think it was Dudley, actually) had a leeway zone of about 2-3 numbers on either side of the "correct" number, meaning a range of about 5 numbers. That would make a 60-number dial actually have about 12 combinations to try out per number. With three numbers, and considering that you just have to turn until you get an unlock on the third one, only the first two numbers matter, meaning 144 possible combinations. I don't know if they still make Dudley locks that way.
With enough time, any combination lock can be unlocked, so locks that require keys, or better yet, fingerprint readers, would be preferable.