Winchester/Miroku uses real US-grown black walnut that gets shipped to Japan for processing.
While pretty, both the butt stocks you depict would have been rejected by Winchester when guns were made in the USA. One has a long knot through the side and the other has a filled knot on the belly of the stock. I don;t mind character, but these are areas for potential cracking and checking if the stock gets rain-soaked.
Nothing is made like it was pre-64 anymore - not even the "pretty good" Mirokus.
*shrug*
I believe that today, nice walnut has been replaced by synthetic for actual hard use. I have an 870 Police with a walnut stock and I'd very much doubt many police forces that purchase newer guns opt for the wood over the synthetic that'll likely take more abuse.
Still, the Miroku stocks look beautifully finished and smooth as glass, and the integrity of the stock surrounding the knot has likely been assessed and addressed, so I have no worry about the life lasting my lifetime and then some.
Finishes of yesteryear that would've been sufficient for hunting and getting dinged up and wet have been replaced by much more suited materials. I love rich deep bluing and fine walnut, but if I wanted a serious hunting/woods rifle for bad weather, common sense would prevail and i'd be carrying a stainless rifle with a synthetic stock.
I love my 1911 for its wood grips and beautiful blued finish but if i were afforded the opportunity to carry a pistol in foul weather, I'd imagine a polymer Glock would be more suited to the task.
I think that gun manufacturers realize that guns made to look beautiful won't be called upon to fend off as harsh of weather as standard blued and wood guns. I suppose the guns of yesteryear including the pre-64 Winchesters were made with the likely possibility that they'd be called upon to work outside. When I see pictures of them they seem to have more plain-Jane hunks of wood on them, perhaps for utilitarian purposes and not for aesthetic purposes like today. Perhaps Winchester of today figured the likelihood of their new line of rifles being used as hard as the old ones was pretty low, so they chose wood with some good looks and character versus sheer strength? Just checked my Marlin 1894 Cowboy Limited, JM-stamped gun and it has a knot in the buttstock too.
Yesterday's utility materials are today's luxury as we have perfected cheaper goods that are more up for the rugged task.
If you think about the fact that a shearling coat or Burberry trench coat for 2,000 dollars was meant for hard farm use or muddy warfare respectively, or that a $120,000 dollar Range Rover would make a rugged off road vehicle, you gotta figure most people would have cheaper goods to accomplish the task and save their luxury goods for the historic appeal or whatnot.
In other words, I love the way the stocks look with the knots and grain popping and whatnot, but I understand the limitations and would grab a cheaper synthetic gun over a thousand dollar lever action to shoot in the rain.