in this post we decided to put a picture from the week of psychology realized in Barmen in 1927.
According to the Associations for Philately and Postal History "stamps Wuppertal" the postmark belongs to a set of several postmarks with advertising:
"Until the merger, there were cities in Barmen only four advertising temple:
24.04.-04.26.1904 handstamp with "space shooter"
28.07.-08.01.1909 handstamp with "XVII. / World Conference / Barmen-Elberfeld
14.09.-20.09.1927 handstamp "Barewo / Barmer Reklame-/Psychologische week
24.02.-03.03.1929 handstamp "Reich Accident Prevention Week
Retired from: http://www.postwertzeichen-wuppertal.de/w_stempelg.htm