Now I do recommend getting your key cut to code, not just copied which transfers all the wear and tear onto the new key. Cutting to code also helps your locks work smoother and last longer. Do you mean by using the lock number? Funny thing is I had the driver door lock in pieces the other day. I want to fit a remote central locking unit and use a solenoid. I meant to jot down the number on the barrel but forgot. I'd had to force off the end cap on the barrel to get into the tumblers as two had broken and were sticking in the shut position. It is only peened over and was easily re-peened. I was spending 10 mins jiggling the key just to open up. The door lock now works fine. It is such and old motor is it worth the trouble of being cut to code?? If I could I'd convert to push button start.