Hi Friends Collectors.
I think the main parts of your frame is original, but the locking system is transforming because it's a fine metal sheet and the time and the rust destroy it. The fastening is modifying too on your model.
I have got the same frame and have got the same problem.
I restore it like original, here the pictures :
This frame is for Lkw or Pkw.
Regards from France.
Stephane