Sadly, this is one window treatment I'll never see in its new home, not even a photograph.  It's a Sheffield valance for a bay window, which has cabinets that intrude into the mounting area.  The three mitered dustboards are flat across the whole valance, but beyond the cutout area, boards extend upwards, sort of like an upside down cornice board, and the valance is attached to the 3/4" part of the board.

A self-microcord was secured with double-sided adhesive tape, to make it easy to control and adjust; then the dustboard cover was stapled over it and down over the back.