I was saving this Paceline article from Bicycling magazine (Jul 1989) for another day, but it seems to fit well here with 7-11 and Hampsten.
Early race testing of Shimano Dual Control prototype?
If so, it seems Shimano changed the prototype mechanism from a "small button atop the (brake) lever" to the well-known inner lever for mass production.
Or did the reporter get this wrong?
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WTB: Slingshot bicycle promotional documents (catalog, pamphlets, etc).
WTB: American Cycling May - Aug, Oct, Dec 1966.
WTB: Bicycle Guide issues 1984 (any); Jun 1987; Jul, Nov/Dec 1992; Apr 1994; 1996 -1998 (any)
WTB: Bike World issue Jun 1974.