Jonathan Ferguson, curator of the National Firerams Center in Leeds, UK, mentions in his book
The "Broomhandle" Mauser a prototype of a Schnellfeuer-Pistole from 1926. Unfortunately, a wrong picture was erroneously shown in the book (p.18).
Enclosed is the correct picture that I received from Jonathan for a book review in a Swiss gun magazine. This pistol is in the National Firearms Center in Leeds, UK.
Alexander