As an addition to his 'field sketching' technique, Pen traveled into North Korea with plaster busts of Western ethnic heads as to teach accurate depiction of physiognomy to his students. After his departure from North Korea, the Pyongyang College of Arts replaced Pen's busts with ones showcasing Korean faces and physiognomy, which remain as a tool used in classes today. This replacement of the busts was implemented as part of the introduction of the “Juche” ideology, created by Kim Il-sung in order to distance North Korea from the Soviet Union and its influence.
