Hopefully Brad can help us Dean.
I agree that the distal segment of the right tube poorly matches the breech (thicker) segment. Tubes were usually made up from 2 or 3 segments.

This is a dramatic example of mismatched tube segments; a Remington 1900 KD with a clear transition (and weld line) from 'Oxford 2 S.J.' Two Iron Crolle at the breech to a 'Boston 2 S.J.' distally, on both tubes.

http://pic20.picturetrail.com:80/VOL.../284854005.jpg

More examples here http://www.picturetrail.com/sfx/album/view/18015717

Drew, Thank You!

Drew
My guess is that the individual straight ribands were made and stockpiled prior to the wrapping and welding step.
The makers identified the pattern by swiping with Sulfuric Acid. This will show a faint pattern. I have noticed that stub twist and Damascus twist look the same with the Acid test. The fine pattern of Damascus twist does not come out untill well in the finishing process. This could explain the mix up in Ribands during the wrapping step. The mix up would not be noticed until the finishing process.

Brad