Sounds like a question for Travel With Guns or another similar service. I bet they will know as well as, if not better than, any bureaucrat that picks up a phone.
S/N's were not needed before 1968 here in the USA, and such Guns can still be bou f ht and sold without them, so this must have come up before.
Please keep us posted!
Excellent suggestion calling a service, I've had less than stellar help from government agencies. Also, I agree this issue must have been encountered in the past given the number of rifles built without serial numbers.
