I actually had to watch this video during metallurgy class back when I was a welding apprentice.
The perfect blend of mild carbon on the inside, martinsite on the outside. The fact that they accomplished this with comparatively intuitive measures as compared to todays standards, its really impressive.
I wonder if you could do a poor-man's version of it by hard-casing mild carbon steel after you've fabricated the necessary pieces to make a sword-like thing.
I may eventually try this to see how well it works.
Well of course those stones can cost up to thousands of dollars seeing as you're dumb enough to use rare large natural stones instead of synthetic stones which are much cheaper, have uniform particle size and density, and are otherwise superior in every way.