Mark Edward Campos, a third year architecture student developed a great graphic on a method to defeat a Rotary Dial Master Lock. Of course the intent of all of this was to find out how a Master Lock works and not necessarily how to defeat it. Essentially, you determine the first number by pulling up on the latch while the dial is rotated. Next, a table of all possible first and second number combinations has been calculated for you. Then you tough it out and attempt the one hundred combinations or so left.
Hack A Day had previously published an article on this method but suggested that using a shim made from an aluminum can is preferable. It is a lot faster. I thought our readers might be interested from a security perspective in this video of the shim method.