FINDING THE LAST NUMBER
On older Master Locks, ones where the arrow at the top is raised, simply pull on the shackle and turn the dial until it catches, that's the third number in the combination.
On new locks with the recessed arrow, there are twelve places the dial will catch if you turn it while pulling on the shackle. Seven of these will catch between two numbers, ignore these, and find the the five that catch on a number. Four of these will end in the same digit, i.e, 1, 11, 21, and 31. The fifth ends with a different digit, and is the third number in the combination.