The tag will only give you very limited information about colour, body style and where it was built.
If you want to know about the car, you really need to get the VIN and order the PHS documents for it. Those will tell you everything it was ordered with from the factory.
If you go to the following FAQ page F.A.Q.s - Data Plates you can decode the '67 data plate. The information provided may be incomplete. I do not see a paint code, and the group codes don't look quite right. As shown, the "23" would indicate that there are no options in the '2' group, followed by an unusually large number of options in the '3' group with some codes listed twice. Did the seller provide a picture of the body tag?
really competent fan base here in this forum. thank you very much this really helps me. I think this Firebird is quite original. But i understand that i need the vin and a phs-documentation to know everything about the car.