The HP 9845B/C keyboard uses switches supplied by Cortron, including the rare double action type. None of the Cortron switch part numbers have been traced for this model.
Keyboard model 02645-60023 for the HP 2645 uses switches supplied by Cortron; this example appears to have been assembled in early 1978. The momentary switches are Series 54; the alternate action switches are curiously the highly unusual “Style A” switches associated with Licon/Cortron Series 555 keyboards. The switches use a non-standard keycap mount that appears to be compatible with Cherry M6 switches. Potentially this keyboard provides evidence that the “Style A” type is also part of Series 54.
Cherry manufactured keyboard model B21E-A601 (HP part 3101-0436-1 REV.G. in this instance) for HP’s 9835 unit. The Cherry serial number suggests production in 1982 or 1983.
The C1405A keyboard uses a capacitive membrane system from W.H. Brady Co.. In Brady’s patent, this assembly appears to be self-contained, but HP’s full travel arrangement includes a rubber dome sheet with carbon-coated domes, suggesting that part of the sensing process was moved from the membrane assembly to the rubber dome sheet. Tentatively this example appears to be from 1989.