@agracier Than ks for the link - also found this one with some more sketches from Gaggelman. I kinda like the sketches vs the colored drawings - but both are good!!!
https://www.msg-encheres.com/en/lot/113394/15018704-gert-gagelmann-active-in-19401
Aha! The very first double image, of a standing lady being given an enema by another lady has a very interesting backstory.
The drawings were made by drawing from a photo session that was made by a Parisian photo studio that specialized in erotic scenes that were still barely legal. So, no genitals in view but lots of breasts and buttocks. The studio was run by Jacques Biederer, an immigrant before the First World War, from what is now the Czech Republic. He set up a photo studio in Paris and gravitated towards producing erotica, mainly naughty photos of bondage, punishments, spankings and one notable enema series.
These photos are all over the Internet, also on some of the Zity albums, mine as well I believe. The photos also served as inspiration for not a few hand drawings and apparently sketches by Gagelmann as well. They must really have struck a chord.
The story of the Biederer Photo Studio (also known as the Ostra Studio) has a sad ending though. Jacques Biederer was joined by his brother before the first war, but being Jewish, during the German occupation in the second war, both brothers were taken into custody and deported to Auschwitz where they were murdered. A sad ending to a tale that branches out in many directions.
https://en.wikipedia.org/wiki/Studio_Biederer
There is also a wonderful book on the Ostra Studio by a fervent Parisian collector of erotica Alexandre Dupouy.
httpshttps://www.amazon.fr/éditions-Ostra-Alexandrep-DUPOUY/dp/B00ZRRNB8O