Howdy
First off, I am always suspicious when somebody says a gun has never been fired. If nothing else, it was fired with proof loads at the factory. Look on the recoil shield to see if there are 'ghost' marks left behind around the firing pin hole from primers and cartridges slamming back in recoil. That is a pretty good indicator of whether or not the gun has been fired.
This 2nd Gen Colt has been fired a lot.
This Smith and Wesson has been fired a lot too. Cartridge heads have left a ghost mark on the blue of the recoil shield. You can also see the beginnings of another mark at the Ten O'Clock postion. This is because as the gun jerks backward in recoil, cartridges that have not been fired yet will also slam into the recoil shield, just not as hard as cartridges that are fired.
I've looked down a lot of barrels, including Colts.
Typically, the hole is first bored all the way through the barrel with a gun drill. This often leaves chatter marks in the bore. Sometimes they are very minor, sometimes they are more noticeable, depending on the feed rate of the drill. Next, reamers are pulled through the hole, cutting the rifling grooves deeper than the bore diameter. (Which is why it is called Bore Diameter.) The reamers remove the chatter marks left behind in the original hole. Since the reamers are pulled through the hole, they often leave minor tool marks running the length of the bore.
With all due respect, it is a little bit difficult for me to see in your photo what you are referring to. It looks to me like some nasty chatter marks located in one location in the bore, near the forcing cone?
If so, they are probably just deeper chatter marks left behind in one location during the boring process. Yes, the quality could be a bit better. I'm looking down the bore of a 1st Gen Colt from 1907 and there are non chatter marks at all. But that was 1907 production.
It all depends on how perfect you want the gun to be, and what the selling price is. You might be amazed how well revolvers with less than perfect bores shoot. I have a S&W Model 65 that I bought used a bunch of years ago with a real nasty divot in the bore up near the front sight. It shoots just fine. I have old guns with pitted bores and they usually put a good spin on the bullet and shoot just fine too.
It depends on the price.
Any idea when it was made? I don't have any 3rd Gen Colts, but the early ones had a reputation for less than perfect finishing. Later they got better. No, sorry I don't have dates other than to tell you 3rd Gen production started in 1976.
Personally, if the price was right, I would not hesitate very much to buy it if that is all that seems wrong.