I just want to pass on something I learned about finding the combinations to Master Locks. I have used the method described in several places here and elsewhere to get the correct combination by first determining the third number. The usual method is to find the possible third numbers and the one with the last digit which is different from the others is the correct one. However, I recently aquired 6 locks which are used in my daughter's school (They weren't stolen, they where given to her by her coach because the combinations were unknown). They are the type with a keyway in the back. I found that the above rule didn't apply. There were four possible third numbers and they all had the same last digit. This meant that I had to try many more combinations, but I eventually got them open. For example, the possible 3rd numbers on one lock were 9, 19, 29, and 39. 29 ended up being the right one. This number really was not at the mid-point of the sticking point and I thought it was a decoy. I guessed that it could be the third number on the basis of the last digit being the same as the others.
I don't know if this is any new revelation, but I thought it might prevent someone from giving up on a lock because it doesn't follow the popular rule.