There are also however slag (silicates, phosphorus, sulfur and metal oxides) inclusions that do represent a barrel defect, and which the apparent silver solder may be covering.
1895 Ithaca Crass with damascus barrels that were being cleaned up for reblueing. Initially just a small pit on the surface of the barrels, quickly grew into what you see here as polishing continued. Inside the barrels are bright and smooth, giving no indication of a flaw.
This looks to be brass brazed ? into a fractured barrel
