Olivetti Praxis 20
The photos below show the keyboard of an Olivetti. Praxis 20 typewriter. The keyboard assembly was supplied by SMK from an unknown series and is one of the keyboard modules that Olivetti did not manufacture themselves. It’s not clear whether SMK or Olivetti instigated the design. The switches use conductive rubber domes over what is presumably a single membrane sheet. The guide shaft for each plunger contains a curious-looking protrusion a little like the prong in spring over membrane keyboards; it is likely to serve a very different purpose. This unit or model is said to have been made in 1983.
The membrane sheet is SMK part number J-F3336-01, with an unreadable suffix letter. The “J-F” prefix is associated with the components of membrane keyboards but is not known to be sufficient to identify the series name.
Photos courtesy of Steve Kuterescz, E.T.ZONE.