See Rumpler

The Bumpler name was taken from a text prior to WII, which had mistaken the name by a single letter.
As we can see further on in this publication, it is "Rumpler".

-Nor was the name "Rumplex" correct, which appeared in this publication's seventh appendix from 2003.

-Both in the appendix as the figure below, these are the correct illustrations of this engine.

“Rumpler”