My husband has a question about his 1989 Suzuki GS 500 motorcycle?

Ok so he bought the cycle and the key broke when he was opening the gas tank. I have called a local Suzuki shop and they advised me they could make a new key by using a number inside the starter ignition. (I was told by some that it could be done with using only VIN) Does anyone know what we really should do should we have to remove the ignition and is there really a number in there? We just thought that the Suzuki place did not sound that confident in what they were saying on the phone.