What is NV_set_window_stereomode?

I’ve been experimenting with stereo on a Quadro 4 board with the latest Nvidia drivers for linux (3123). I happened to notice that there’s an extension in the Nvidia OpenGL header called NV_set_window_stereomode. There also an entry point called glSetWindowStereoModeNV which I assume has something to do with this extension. I’ve searched nvidia’s web site and done a google search and can’t find any documentation on it. Anybody know what it does and whether it works or not? My Quadro 4 doesn’t seem to support it. Does any nvidia board support it?