The BladeForums.com 2024 Traditional Knife is available! Price is $250 ea (shipped within CONUS).
Order here: https://www.bladeforums.com/help/2024-traditional/
Barkeepersfriend, it has a chemical reaction with the metal and literary eats it away.
A little water, BKF, and a nylon brush will make them look newer than new just rinse well you don't want to leave any cleaner on the stone. No ill effects except a clean stone with little effort. After using spyderco ceramics for several years I found it to be one of very few products that properly clean ceramics, its also works on other types of stones too.
Scotchbrite pad. Add a bit of the aforementioned Comet if the build up is really bad.
DancesWithKnives