Robert: I did my best to enhance the image, but will need a high resolution ultra close up to 'read' the pattern. I think it's Laminated Steel
Barrels were made with 2 or 3 tube segments, the thicker at the breech, and it's not too uncommon that the maker didn't quite match the segments.
W. Moore with two different Laminated Steel patterns, the thicker at the breach. The patterns join in a straight line weld suggesting that the barrels were formed as tubes with one tube flared, the other coned and then butt welded together.
Leighton Stallones' Greener with different Laminated Steel segments
L.C. Smith with slightly different Chain Damascus segments
Threaded Mode