Mitsumi standard mechanical
“Standard mechanical” is the provisional name for Mitsumi’s standard size discrete metal contact switch modules. This name is in contrast with the “miniature mechanical” switches that are distinctly reduced in size.
Standard mechanical switches came in two sizes: the older type 1 switches with tall sliders, and the presumably DIN-compliant type 2 switches that share the same negative post design with Alps SKCL/SKCM.
Further detail on some of these switches can be found on the following pages:
Standard mechanical switches use switchplates: discrete switch contact modules that can be inserted and removed as a self-contained unit. Just as with the Alps design change from SKCC to SKCL, the switchplate design in type 1 and type 2 switches is completely identical and the switchplates are fully interchangeable between switches:
Depicted above are, from left to right: type 1 linear, type 1 latching, and type 2 latching.
The switchplate colour appears to have changed over time. type 1 switchplates are a medium blue colour. Type 2 switchplates came in two colours: a deep turquoise/cyan colour (a slightly greenish blue) very similar to the original blue, and unpigmented plastic (“clear” or “colourless”). The two type 2 colours can be seen in the photos below, depicting ostensibly switches from the same packet of Apple service parts:
rzw’s Apple Extended Keyboard II shows the opposite to what I have: a colourless switchplate for the tactile switches, and a turquoise switchplate for the latching switch.
The exact sequence of switchplate colour change is not yet known for certain, but it would seem reasonable to assume that the turquoise switchplates came before the colourless variety. The latching switches used in the Apple Extended Keyboard II demonstrated another variety: the upper shell of the switch could be either deep blue (as in my collection, shown above) or colourless (as in rzw’s AEKII photos). Because the type 1 latching switches were coloured differently to the linear switches, there is a suggestion that the wholly colourless variety came later, and that Mitsumi were cutting costs through avoiding unnecessary pigmentation (the linear switches are already a different shape).
The above still does not account for the anomalous type 2 switches with colourless switchplates.