Hello Dj,
Leica serial no.38624 was originally a 1930/31 Leica 1(model "A") fixed lens and must have undergone a Leitz conversion to a Leica 11 (model "D") interchangeable lens with coupled rangefinder sometime after 1932.This was quite a common practice for earlier cameras to be upgraded to the latest type in the 1930's and 1940's and Leitz provided an official upgrade service to this end.The 50mm F2.5 Hektor lens was the first fast lens produced for the Leica camera and was produced from 1931 to 1937.It was installed on some fixed lens type Leica 1 (model "A") and due to only limited production of the Hektor fitted Leica 1's these are now very collectable cameras.
The 50mm Hektor was designed using six elements in three cemented pairs and total production was 10,300 (approx).The lens is now a collectable Leitz lens but it is not noted for its performance as a good lens for use on the Barnack screw cameras.
You could check with the "Hahne" list if your camera started out as an original Leica 1 (Model "A") with fixed Hektor.
Kindest Regards,
William