Hans-Wolfgang (Pierre) Gassmann
Since the family was German, it is likely that Pierre is not his original name. An unsourced (as at 18/12/2016) article on Wikipedia says that he changed his name from Hans to Pierre.
His mother was married to Max Gassmann whose death announcement in 1915 lists his children as Klaus-Ferdinand and Hans-Wolfgang; "Pierre" must be one of these. An article about Pierre Gassmann includes a photograph of Klaus and Pierre Gassmann in 1921, which means that "Pierre" must be Hans-Wolfgang.
photographie.com - article including photograph of Klaus and Pierre Gassmann in 1921 (saved for posterity by archive.org);
fr.wikipedia.org - name change;
de.wikipedia.org citing tumblr.com and wissen-digital.de says he was born in Breslau where his mother had an X-ray laboratory - this must be Selma Gassmann.
This record was last updated on 18/12/2016 at 17:00