This old Corbin padlock was about to be dissected and rebuilt as I have done with similiar locks, but upon close inspection I saw that the lock was only a three lever unlike my Corbin Railway Express 6-lever padlock. When I attempt to defeat a lock for picking or decoding, I always look for design flaws. This lock just so happens has such a flaw, and that's the drain hole at the bottom of the lock. I knew that if I could pick the lock, the levers would lock in place where I might possibly decode it and make a key.
I picked the lock by inserting a tension hook tool in the key hole. While applying tension clockwise on the internal mechanism at the bottom of the lock, I inserted a second tool through the drain hole to manipulate the levers. I knew that the levers were in picked position once they got stuck, similiar to what pins do on modern day tumbler locks.
After I picked the lock open, I made a special decoding tool consisting of two overlapping wires that are inserted through the drain hole. One of these wires has a circuliar end which curves around the center pin in the key hole. The second wire has a ninety degree tip which is inserted until it hits the face of the lever that I'm decoding. The opposite ends of the two overlapping wires are measured using the tip of my dial calipars. I calculated the distances from the inside surface of the key hole center pin to the face of each lever and translated these measurements into depth cuts. I made a key blank, smoked it with a candle to get my reference for the first cut, and preceeded to make a perfectly working key.
Corbin, BOARD OF EDUCATION. 
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