Krieghoff Drilling Information Sought.

[Smoke & Recoil]

I have read many times about European shotguns having 65mm, 2-9/16" or
70mm, 2-3/4" stamped on, but this ole gal has nether. I know it's 16X16X8x57JR (IR). Am I missing it somewhere ? Any help would be great.
Regards.

 

[Smoke & Recoil]

More pictures.

 

[Smoke & Recoil]

Last picture.

 

[Jim Watson]

It isn't specifically marked 70 so it is 65mm, 2 9/16", that is the default.
16.1 codes the bore diameter, near 16.99mm, .669".

 

[Scorch]

You have a pre-WW1 drilling in 16 ga/7.9X57 (German Imperial proofs). The 2-3/4" 16 gauge shell did not exist back then, it was introduced between the two world wars. FWIW, the rifle barrel groove diameter is .318".