Donnerwetter! Another mistake! Well, let's be positive: another mistake corrected!
I thought that the metal Nasenflöte that was advertised in (almost) any german catalogue in the 1920-1930's was the one made by PaBru, the Paul Brunner's company in Brunndöbra.
The omnipresent no-name german metal noseflute and the Paul Brunner's one:
The no-name german Nasenflöte:
But if you look well at both engravings, you'll see the shape is not the same, particularly for the airway cap and the nose shield.
It could have been a drawing artefact. But I found a record of the Metropolitan Museum of Art for a german nose flute. There is no picture, but the record says the instrument is in metal and dates of before 1941.
Much more, the description says:
Donnerwetter (again)! The "water pump" was the PaBru trademark! The exact mark that appears of the Fanfare instrument as on the flutes and kazoos, playing with the rebus around Brunner: Brunnen means well, spring, fountain in German.
So, there was "another" german nose flute, stamped with a "water pump" and made by PaBru. The question remains to find who produced the no-name german flute, and where... Klingental district too?