Rifles built in Northern Europe tend to use Linseed Oil (flax oil) in one form or another. It was and remains a local material which works well both for restoring toughness to old wood AND (in its truly BOILED form) for FINISHING wood.
ALL British firearms have used Linseed Oil for centuries, as have German and other Continental weapons. If you buy the best German stock finish today (Schaftoel from Mauser-Werke), you re buying Linseed Oil with their proprietary red colouring.
TUNG oil, which the Americans prefer for their military stuff, is from Asia.
I have the remains here of what once was a French 1855 Musket. The wood was so dry that it was turning white and was VERY lightweight: not standard at all for what once was a very prime chunk of Walnut. I ripped it down to bare wood, slopped on the RAW Linseed Oil and watched it drink it all down. The end-grain of the Butt was so dry that the oil would be absorbed in the time it took to put more onto the sponge I was using! When it finally slowed down, the wood was darker and a lot heavier, so I gave it a coat of appropriate stain, wiped on and wiped off, more Raw linseed oil to get it into the wood, then finished off with just enough Double-Boiled Linseed Oil to bring up a glow.
It might not be original, but the materials were correct and it looks a lot better.
Next step is to electrolyse that rusted old bore and, if it comes up half as good as the last one I saw, it might be a shooter.
If I can shoot just ONE Dinosaur with it (waste to use a .75 on anything smaller!) I will regard the 100-buck Wallhanger to be fully PAID FOR.