The 123 over 431 marks show the gun was the 431st gun proofed at that proof house in January 1923. German proof mark crown-over-S indicates smoothbore, crown-over-W is some degree of choke (usually lots), crown-over-U is the final inspection mark. 16/1 indicates that at the time of proof the bore diameter was between .669-.676", the next size up from standard 16 which ran from .662-.668"; 16-in-a-circle shows the gun was chambered for 16 gauge cartridges, the absence of a "70" mark anywhere shows the gun originally had 65mm (2-1/2" or so) chambers.
Nice looking gun. It's also always a pleasure to see unbuggered screw heads.
Last edited by Steve Meyer; 11/27/06 06:05 PM.