MS-CS Chair by Keith Muller and Michael Stewart.
These things are entirely subjective, but to me, this is THE archetypal bent ply chair. Certainly, there are more elegant designs (Charles and Ray Eames and Arne Jacobson come to mind, though their all-wood creations never achieved the same elegance as those with steel legs) and more groundbreaking/original forms (Alvar Aalto, Thomas Lamb, Frank Gerry, etc.), but none of these classic designs achieved the same ease and familiarity. With plywood and four screws, Muller and Stewart created a chair that is both strikingly honest and highly functional: comfortable, durable and stackable. This particular chair is from the collection of Christina Zeidler at The Gladstone Hotel. As far as I know, the MS-SC was never produced in black, so this one must have received a custom paint job at some point. -Michael Erdmann
I found this chair at the excellent The Canadian Design Resource Blog, but it seems disappeared since.