Hello LawrenceN, thanks for the pictures, you took some good ones...
Here's what I'm seeing, and mind you, I'm no expert...
To my eye the barrel appears to have been shortened at the muzzle at some time as I believe I'm seeing cutting scars on the muzzle. This may have been done for several reasons (all conjecture) of course;
1. It may have started life out as a Target rifle with a False Muzzle and someone may have wanted to turn it into a hunting rifle, so they shortened the barrel? (If so, what a shame).
2. It may have very well have had a longer barrel and someone may have tried to add a False Muzzle and it didn't align it correctly (if it was an after thought) - or - it may have been drilled for a False Muzzle and perhaps a bit broke - or - the holes on the muzzle flats were not drilled straight not allowing a False muzzle to be used so perhaps the idea was given up on adding / making a False Muzzle and the muzzle was cut down to simply offer it as a lighter target / hunting rifle?
I expect only the maker can tell us what the 80 stands for on the muzzle, or is it 08, depending on which direction it is to be viewed from?
Regardless if any of the above conjectures hold true, it is still one heck of a piece of history that I will say again it would be great to know this rifle's history.
I expect Recoil could be one reason for the stock fracture, or the rifle could have been dropped and just hit wrong on the butt end of the stock which may have caused it? That's an awful heavy barrel on that rifle.
Again, I hope we can find more out about this rifle and its history. A remarkable find that just needs a paper trail. Where a person would start, I have no real idea, but I thank you for letting us have a look at this piece of history.