I've come across them before, thirty or more years ago. Admittedly not micro-sized slats, but approx 1", the outside DG panel being conventional, the inner panel being single-pane but hinged/removeable and the whole construction made in extruded aluminium. Rather neat, very heavy, not terribly reliable and expensive as hell. Looked really good though; and the only place that could afford to have their entire office block fitted with the system was the local Electric Board. Of course.