One o'clock. While it's a little cheat, the limited edition from Vacheron Constantin Les Historiques line, the Historiques American 1921 has a cushion-shaped case with a crown positioned at 1 o'clock. However, if you'll read the dial, it's on 12 o'clock. Either way, it doesn't make it less interesting for me.
- Historiques American 1921
I still miss crown positions at 5, 7 and 11 o'clock. You're more than welcome to send your links to unusual and interesting crown positions, and I'd be happy to add the to my collection.
The full collection of crowns' positions is here at http://live.prokhorenko.us/2009/08/watches-are-all-about-crowns.html