Damascus anomaly

[ArtS]

As to the bore, it is definitely marked 17.8, which is very close to 0.700". The entire barrel assembly profile is very close to the outside dimensions of a W&C Scott 8 gauge from 1872 which I own. I suspect that Galand may have made one gun for 12, 10 and 8 gauges, so the outside would have been duplicated and fit the same action. I think the 10 x mark may be related to the 10 gauge chambering (10x being a long chamber?). As mentioned, the chamber wall at the back is over 0.36" at the thinnest. Based on the outside taper, the thickness at the front would be around 0.32", and near 0.5" under the octagon corners.
I will try to measure the length with a 10 gauge chamber gauge. It has enough length to measure longer than 3-1/2".

I don't know if a tracing will work, but I will try or maybe make a scketch.