The new Selmer Series III has the option of an altissimo facilitator key, which opens a secondary vent on the neck. It's pretty rad. I wasn't able to play with it.
The "helper" key is called "Harmonic" in Selmer literature. Not only has it been available for several years, Selmer says on their website that it was available on the Mark VI. (Of course, YMMV on the accuracy of Selmer's website.)