Nothing gives the flavor of the Classic Moth class more than to wander around Pugh's lawn at Elizabeth City taking pictures of transoms. There cannot be a more diversified racing dinghy class going anywhere in the world. Here are some (not all) of the various sterns at the 2013 event.
The Skip Etchells designed Connecticut Moth (designed 1948).
The flattish transom from the Olympic Europe.
The early 1950's Mint design (boxy, slightly rounded).
The circular transom of the stock Mistral. Builder/skipper is Mike Parsons.
The flattish transom of the one-off Lane Reeves modified Savannah Mistral.
The modern looking transom of the 1960's John Shelly design (definitely one of the innovators during the 1960's). I have been told that he tried to patent the distinctive inward curve to the topside panel at the stern.
For further study, George A. has on-the-water photos of Classic Moth transoms over at his Mid-Atlantic Musings blog.