Larry is right. I have a VL&D/Sauer from around 1901 which has a 12 in circle with a 70 stamped into the extractor face with 2 3/4" chambers.
That said the odds are this one does have 65mm (2 9/16") chambers. Also realize that even with the Nitro Proof, it was proofed to CIP specs, NOT SSAAMI.


Miller/TN
I Didn't Say Everything I Said, Yogi Berra