It is an old one. Right now, it is dirty, but it is original. It wears its years and history on the outside for all to see.
Is it all there? Anything broken?
Restore it and you will have a pretty rifle. $$$ and a lot is lost.
This one is not rare, nor is it particularly valuable.
But it does have the charm of a heavy patina.
A good sympathetic cleaning is what it requires.
Remove any active corrosion.
Gently clean off the dirt and oxidisation.
Stabilise the wood.
You will then have a clean old rifle, nothing lost.
I love these old guns and enjoy bringing them back into presentable condition.
But many of my projects end up being more preservation rather than restoration.
Too much of an enthusiastic cleaning can ruin things as an antique.
That patina has taken years to form. An old rifle should be allowed to look old.
Remove the signs of abuse and neglect, but leave it looking its age.
So it all depends on what degree of restoration you were wanting.
How do you imagine it looking when restored?
Looking like an antique, or looking like new?