What you are referring to is case hardening. AFAIK, a quality cone or any other high grade part would be milled from solid billet. It would have the same hardness throughout. The billet would presumably have been forged making it more expensive, whereas case hardening would have been created by heating and cooling — that is to say tempering. If I'm wrong — someone burn me down as I'm retrieving stuff that my Dad taught me many decades ago.

What does this mean to Dawes-man?
Well you have nothing to lose, so I'm gonna suggest something that reminds me of something my uncle told me back in the Cretaceous. In Britain during WWII he worked 12 hour shifts making pistons for Rolls Royce Merlins. (They powered Spitfires, Hurricanes etc). To wind down after work, he'd go home and grind a crankshaft of an old Riley race car — with a file! Now this guy was old school craftsman. They don't make them this way anymore. You would be on a big learning curve. But lets try:

His method used machinist's blue and a repeated process. He'd file down the crank bearing surfaces turning the crank in V-blocks. Then he'd assemble the blued crank with the shells and torque down the caps. Then he'd turn the crank. Next he'd pull down the bearing caps, the shells and stuff and put the crank in the V-blocks and file away the blue high spots. Then he'd repeat the process. No one can do this anymore — or wants to. It worked for him!

Now for you ... you can use a fine rat tail file. You need a small vise. You file as best you can and as close as you can to the center of the bearing track. For the inside race you can use a Dremel type tool [Dai shin sells them] and an appropriate sized and shaped stone. Blue up the cones and races and assemble them on bearings with no grease. Rotate them and see what comes out. Trial and error. It may drive you crazy, or you may just ace it enough to make them work.

BTW: You may know all about Kamata — a few stops south of Shinagawa, and just before you cross the river to Kawasaki? If you need a machine shop to handle this problem, get the Keihin Tohoku to Kamata Station. Walk out the front and turn east. You will leave the busy high street and be following the river ... or close to it. There is a very winding, narrow road about 100 meters to the west of the river that is the backbone of the neigborhood. It contains the local mom-pop shopping. That whole area is — or was 15 years ago — full of family-run, precision machine shops. Typically, the family lives above the shop.

This kind of stuff is their forte. (They make hydraulics for the shinkan-sen and so on). This kinjo has been considered the pride of Japan. After the bubble, the government tooks pains to prevent these crafts families from being ruined. (Let's hope they succeeded).

You might find someone willing to make you a new set of cones. After all, if they set up the lathe to make one, they can make more. Or maybe they can machine the old cone and mill the old race for oversize bearings. Just a few thoughts — extreme but that seems to be where you are heading.

If it all seems too much, my LBS here in Sendai has some MKS pedals that do look in character. Your LBS will have the same catalog.

Good luck — and look me up if you get to Tohoku. You can use one of my rides.