Heiko, I don't know about your particular example, but the straight lever could be original. As far as I can tell, the curved lever was first fitted to civilian and military production for 1938.
Certainly the 1938 parts book shows a lever numbered 8955 instead of the earlier 3625. The illustration is a plan view so it's difficult to be sure, but photographic evidence backs up a 1937/38 changeover date.
I'd say that the straight lever is probably harder to find....but it will indeed make gear selection even more of a lunge !