The Master Lock brand 40-digit dial combination lock can be decoded from its 64,000 possible combinations (40^3) down to 80 possible combinations. You can mechanically find the last digit of the combination, which combogen uses to calculate those 80 potential combinations.

In order to find the last digit of the correct combination, start the dial at 0 and pull out firmly on the shackle, then begin rotating the dial and feeling for areas where the wheel seems to stick. The wheel will stick at 12 different points around the dial and move between approximately two digits at each of these sticking points. Record the central number at each of these 12 sticking points. For example, if the dial sticks at one point between 3 and 4, record the number 3.5. If the dial sticks between 11.5 and 12.5, record 12. When all the numbers are recorded you should have 7 half-digits (e.g. 3.5) and 5 whole digits (e.g. 12). Discard the 7 half-digits. Of the remaining numbers, 4 should share the same last digit (e.g. 8, 18, 28, 38) and the fifth number should be unrelated (e.g. 12). Discard the four related numbers and you are left with the last digit of the correct combination. Plug this number into combogen to generate the 80 possible combinations.

GitHub project page: combogen
Download latest version (v0.2): (gz) (bz2) (zip)