Something I spotted the instant mine arrived — the massive asterisk symbol (which I love). I recognised it immediately as matching the corresponding keycap of my Oriental Tech OK-100M keyboard from 1991 or 1992.
Here's a comparison — NIB 1991/1992 keycaps top, group buy keycaps below:
So there we have it. 22 years of double-shot production! I've since realised that a lot of keycaps match exactly, including the Focus FK-2001 and at least one OmniKey. Other keyboards match sufficiently to suggest the same keycap OEM.
Looks like we've been using their doubleshots for a long time without realising who they are.
Of course, it could be that another company set up doubleshot tooling with the exact same font, symbols, spacing etc, but that seems rather unlikely. Most keys match, including the exact size and shape of the arrows on the arrow keys.