Lots more info in these links.
http://www.pacificrimcamera.com/pp/leica/sm/smid.htm
http://www.cameraquest.com/classics.htm
Cameraquest links has a tab with serial numbers and yours is definately a Leica II D without the slow speed dial on the front plate as in the straight II.
Back in those days it was common for slow speeds to be accomodated on a seperate dial.
Don