Mostly from English sources... there were at least 300 heating done per tube. A set of barrels would take 3 men two working days to complete. In conversations I have had, I have "heard" a lot of speculation about auto-hammers, etc, but no one has been able to document their use by the damascus makers...
I am guessing... the small "flaw" could simply be an unevenness in the original pieces that made up the billet. A bit of iron over laps the steel where it shouldn't.
There is so much more work to do. We really have not documented, speculate yes, why it all stopped. Was it the rising labor rates, the lack of raw materials, a shift in the economy, buyers simply stopped buying damascus, people simply stopped buying doubles, take your pick....
How important was the American market? Did the tariff wars in congress have an impact on the trade? If they did and the Belgians were the winners, who lost? Was there a Spanish or Italian center for damascus barrels? Who were those makers? We see German guns with damascus tubes. Where the Germans buying the tubes or making their own damascus.
Many other questions....
Pete