Likely someone's license plate number put there in respose to a tip in an ancient popular mechanics article...so he could ID the cap after forgetting it at the gas station. Never mind that it would be hard to drive a Model A without noticing you forgot to put the cap back...
Canadian postal codes start with V: such as V0P 1G0. However, I suspect this is not the case. Maybe a bank security box no. Millions hidden?? Find it!! Share!! Me!!!!!. Good luck, Wayne.