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Low water marks

This is a list of the earliest use of each of the terms or concepts listed, as currently known. This list is only a personal memo and is neither exhaustive nor definitive: it will be revised as earlier examples are discovered or indeed rediscovered.

Term Oldest usage
Buckling rubber sleeve 1970, US patent 3767022 (granted 1973 to the Singer Company), “Return spring key stem boot” (used on optical beam keyboard)
Mechanical 1971, Electronic Engineer magazine’s “this is your keyboard reference”
N-key rollover 1971, Electronic Engineer magazine’s “this is your keyboard reference”
Optical beam keyboard 1970, US patent 3767022 (granted 1973 to the Singer Company)
Tactile feedback 1970, US patent 3644855 for Cherry reed switches (as “tactile feel”); as “breakaway feel” in US patent 3767022 (also 1970)