I'm truly stunned by the amount of information you chaps can glean from all these marks!
I've taken a couple more images of the barrel ends and rib, the underside rib looks far better fixed than the top one which has a noticeable smear of solder at the end. Might they have been shortened? The barrel lengths measure 74.5cm so 29 5/16".
The rib towards the stock end has some noticeable 'crimping to it' which I assumed may have been down to it being in a vice at some point? Hard to say if they're squash marks or heavy dents.

Underside of barrels at end
https://flic.kr/p/2icqfTr

Whole top rib
https://flic.kr/p/2icqfTg

dints to rib at end

https://flic.kr/p/2ictPp6

I've sent Her Haggards an email so eagerly await anything he can add!