The first thing people marvel at when they see the furniture of the young duo Sebastian Herkner and Reinhard Dienes is its industrial, institutional cool — bare wood against metal against richly colored glass, in shapes evoking old spotlights and torches and desk chairs. The second thing is how these hip, talented designers — whose first collection this year caught the eye of Wallpaper, DAMn, and Monocle — landed in Frankfurt, a middling city of 650,000 without a glimmer of Berlin’s cachet.