They look like shine through. I hate shine through (except on the Apex Pro. Caaaan't look awaaaay)
I don't believe that any of the ones that I ordered were, or the ones in the link I included. They do make them, but only in limited options that I could find. I wouldn't want them like that either. These looked, to me, like laser engraving or something.
https://www.reddit.com/r/MechanicalKeyboards/comments/1jnbsr/why_i_wouldnt_recommend_zinc_key_caps_photos/
they tarnish pretty easily. if you could get a blank set maybe it'd be okay.
I remember the ones I had were from 2012 shortly after feng's gb, but not a full set just a few novelties. (the shiny gold ones of course)
as long as you know what you're getting, it's fine to play with since they're pretty cheap, but you get what you pay for.
I like things with a good worn look to them, though that does look pretty rough. The K65 was already used, with some scratches, and I decided to not even sand them back to a cohesive brushed finish again. It adds character. Maybe I should clear coat them or something then though. I'm surprised they would make zinc keycaps without some kind of surface finish. Maybe that's changed since then?
Honestly, personally, I can't see how metal keycaps could possibly be worth any more than what these cost, if they're being cast. And if casting is possible, there's no reason to machine them anyway. I wouldn't be interested in anything that would cost more. The value wouldn't be there.