This discussion has been great in improving my understanding of serial number anomalies. It makes good sense that barrels were numbered when they came to the factory and that frames were numbered later to the barrels to which they were fitted. Thank you for this good discussion. On the proof mark question, I have had Damascus barreled Lefevers with no proof marks, Belgian proof marks
or hallmarks, and one with a Birmingham proof mark. On fluid steel barrels, once tubes less expensive than Whitworth and Krupp were introduced, I recall another proof mark of a Belgian maker or distributor of fluid steel tubes. I do not remember the specific letters or symbols.
