It is indeed an original party badge made by Gustav Hähl.
It looks to be in very good condition.
The pin plate is NOT coffin shaped but a nice oval in the original raised area.
Below is the Coffin shaped pin to be wary of...
All the best
You are of course absolutely correct, Wewelsburg --- perfectly fine original badge with what I would class an earlier style attachment as compared to the typical perfectly machined round pin plate ones usually sees on M1 badges. Taking into account the obverse design, attachment and transitional style reverse markings I would say it's an early badge from this period.
Thank you for your educating posts! Thats exactly what I need and are seeking for.
I think that i'm willing to give about 60 dollars for it.
No doubt a good price --- congrats!