electroplate is generally nickel or chromium
That's only true because electroplating is usually done for corrosion purposes, which nickel/chromium handle better than other metals (steel, etc.) Also, "cast iron" is really steel with a lot of carbon to make it euctectic. That's why it's brittle. It's often electroplated.
Since these are (apparantly) Zinc as a base, they can be electroplated for aesthetic purposes, and they can use many metals. For example, I have personally electroplated copper (which "might" have been from a US penny) onto Zinc (which "might" have been on a US dime). It didn't work out very well (due to the activity coefficients of the metals involved) but it did work. Also, Gold and platinum are often electroplated onto semi-metals for usage in SEM. (sputtering and/or evaporation are used for other, non conductive samples). IT could be anything, really.
electroplating only coats maybe several hundred atoms thick (but it really depends on the process and how long the plating is). if ABS keys get shiny from the abrasion of typing, there's a really good chance it will also wear down the electroplating film. maybe OP might want to check to with the guy making it and ask him how long he plates these keys for.
You can electroplate a LOT more than 100 atoms with higher current, and more time (you're right though: it really depends on the process) and it's usually pretty this to save time and money (because it's usually done to keep the more active metal from corroding). Since this is aesthetic, it really could be anything.
That's one reason I was leery about this: I didn't want to wear through it, but depending on the composition of those outer metals, it really could be pretty resistant to finger wear. I don't know for sure, but I'd expect it to be better than ABS. They do use metal keyboards for long-life. It'll still wear from you putting your fingers on it, but I'd expect it to be less.
At any rate, I'd not let worries of that impact my decision. Metal keycaps man!
