It’s definitely not an “official” thing, but I have found variances in the surface texture of GMK sets.
There is a nicer texture that I find to be higher-end, that exists in some sets. This texture is kind of like pumice. It’s porous and grippy, a mild eggshell texture that exists at the keycap surface.
Some other GMK sets, though, feel a lot more “uniform” in their surface-texture. That is to say, like flat plastic. No ‘grippy’ surface at all. The “good” texture is a creamy-smooth, mildly grippy eggshell. The “bad” texture is a kind of smooth flatness.
The differences are subtle. Not substantial. But they are there. The sets that I find to have the slight eggshell are:
Honeywell R1
9009 R3
Shoko R2
and the ones that have the more flat, featureless texture are:
Oblivion R2 Monochrome
Modo R2 [a little more grippy than Oblivion R2]
Solarized Dark [somewhere in-between the two types]
The difference between the two types is slight. But I can feel it. It’s as if the “lesser” surface textures have a sort of ‘pre-shine’ effect.
Some DCS sets, when new, have the same “good” texture as GMK. But not all GMK sets have that exact texture, is that I’m saying. I think it’s a minor batch variance issue, maybe something GMK doesn’t notice. Might have to do with the plastics used in some sets [e.g. Oblivion] versus others. Maybe GMK’s classic-era colours are more likely to produce that nicer eggshell.
It’s not a big deal, barely perceptible. But not all the GMK sets are produced equal in my view. This doesn’t even go into the older GMK sets vs. newer, which involves other issues. When you wait 2 years for a set of keycaps, you might notice subtleties between sets.