Lohff & Pfeiffer comments to the model The Buffet Crampon S 1 used to be the little brother to the professional BC 20 and was produced from the 1960 until about 1985.
The bore is similar to the RC and both models were build for 442Hz. If you come along one, dont be surprised how good it sounds. The biggest difference compared to modern clarinet has less to do with the design then with the way it was build. The wood was naturally aged and the majority of keys were casted, which was the technology of the time. They were less precise then modern keys. If a BC 20 or S 1 is properly restored, got new rods and screws it can be an excellent instrument.
The S 1 was marketed in Europe and Asia. Instruments with a serial number starting with F, are built for 442Hz. The sound is full and round. Older instruments often have a sharp pitch. This can be corrected with a bore replacement. See also LP bore restauration.