Mad for Mid-Century Door Knobs

As any mid-century enthusiast does, I watch Mad Men and droll. My latest in-show obsession is a rather small background piece, the escutcheons on the office doors (the square door plate behind the knob).
I love the circle knob contrasted with the square plate. I'm already picturing how good something like that would look on a Crestview Door.

Update:
I found a modern version of the Mad Men door knobs.