SA keycaps come from the IBM Selectric I and II typewriters, as well as the Apple II. I think XDA is just a modern profile developed relatively recently, but it is relatively similar to DSA, which I think also goes back decades.
I think you're also right that IBM is behind the OEM profile, which I think was originally used in the Selectric III
DSA is basically just low-profile SA caps.
And also not sculpted, right?
Interesting. I was thinking of PCs and terminals, but I forgot to go one "generation" back. huh.
And oh my gosh, was there ever a product line that insisted on getting uglier as it went like the Selectrics?
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