What magdyno is this: pre-war, war or post war?
On the brass strip this code: MO1.4 46011B AC20 144, and an arrow pointing downward. Is this the correct type for my 1942 WDm20 ? It still needs some TLC...
And I need a short dynamo, for my all-LED bike!

That is a post war mag body Hans. On the pre-war and wartime bodies the curved part that the dynamo sits on, continues right to the drive end and doesn't have that waisted section over the pick up. The rotation sounds right. Anti clock at the drive end. Ron

email (option): ronpier@talk21.com

I agree with Ron, however it is a nice January 1944 BSA M20 brass plate attached to it.

Rob

email (option): robmiller11(a)yahoo.co.uk