The Top Key

By Xah Lee. Date: . Last updated: .

The Top key first appeared on SAIL Keyboard around 1970.

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SAIL Keyboard

It is like the Shift key, used to input Math Symbols ∞ .

Then it appeared on Lisp keyboards

lisp knight keyboard-s339x184
Knight Keyboard
space_cadget_1st_gen_gg3nn-s250
Space Cadet

Seems, after the Space Cadet, the Top key disappeared. But the concept is picked up, as Apple's ⌥ option key [see Mac Keyboard Viewer] and AltGraph key. [see Alt Graph Key, Compose Key, Dead Key]

Xah Keyboard Guide