Brief notes on Tai-Hao switches.
Reversible switch bases
alps.tw Type T2—mid-era Tai-Hao APC series—shows an interesting characteristic: the base is reversible. I figured that there were two possible reasons: DPST, and ease of assembly. DPST seemed unlikely, and I noticed that these extra holes were not present in the older APC-branded switches with wide click leaves, and neither are they present now.
I put this curiosity to Felly Du, my contact at Tai-Hao. A Tai-Hao engineer explained to him that the reversible base was introduced when increasing demands led to the introduction of mechanised switch assembly. It wasn’t the humans who had been manually assembling the switches who needed assistance, but rather the machinery that was introduced to fill this role. In fact, at this point, both the switches and the keyboards were being hand-assembled.
Improved machinery later removed this requirement, so the second pair of holes was removed.