A 16ga with original 65mm chamber will have the 16 in a circle. If it has a 16 in a circle and a 2 3/4"(70mm)chamber it has been rechambered. If it was rechambered and re proofed in Germany it will have new proof with 16 and a 70, and depending on when it was done, it will have a crown R (repair)proof.
Mike