I'm trying to confirm the identity of what I think is a 1952 CB Avant-Courer bilaminate. I was going to see if someone could identify the year from the serial #, but I can't locate the number. I do not find it on the BB shell or the rear dropouts. Someone suggested that ot might be on the steerer, but before I pull the headset, can anyone suggest an alternate location? It would seem odd the put it in the steerer only, since that would only identify the fork. How many digits are in a CB number?