I generally call this switch "Prototopre". I've seen it as early as 1982 in some Epson/Seikosha keyboards.
Topre, didn't even start looking into office/business equipment until 1983, but the designs are very similar. My theory is that either some engineers that did the original design or used it as a base for their own (more reliable) switch.
My current theory is that it was created by Brother as some keyboards have "Brother-like" model numbers on the PCB. But not all of them. It may even have been some independent design firm for all we know. Also, the only patent reference I've seen to this switch is also in a Brother patent:
http://www.google.com.gh/patents/US3900712 (1975).
Some later IBM RT keyboards used a membrane variant of this switch that was very clearly. These are more clearly shown in patents.
This list even includes a few keyboards I haven't posted yet
Prototopre
DSC03481 Q603A
DSC02895 Burroughs B25 K2
Untitled Seikosha 8620
Untitled IBM RT E57888 6298389
Brother "Topre-like" Domes
DSC_1382 Unisys T27-K5
Note, the graphite pads. Also, Burroughs became Unisys when it merged with Sperry-Rand (Univac). Also note that the mylar membrane supports "both" contact and capacitive switches!
IBM RT E57888 6247440
Uses a mylar membrane closer to what the Model M uses.
Oh, and I have at least one more different Epson keyboard that has this switch (but it's somewhere in my "take photos of" pile

)