A familiar SDR unit marking in the Ma.K universe, the devil's head first appeared as one of the decal options included with the Nitto Gustav kit and is the insignia of the 401st Armor Hunting Soldier Battalion,1st company.
In reality this iconic Luftwaffe symbol (sometimes depicted on a white shield, yellow shield or even no shield) was commissioned by Hans-Ekkehard Bob when he took over command of 9. Staffel, III Gruppe, JG 54 (a typical aircraft of this unit can be seen here) Seeing this portrait of Hans-Ekkehard Bob makes me wonder if he was one of the models for the Gustav pilot bust?
"Hans-Ekkehard Bob was born in Freiburg/Breisgau, Germany, and grew up in the village of Staufen. In 1936 he joined the Luftwaffe and after training, flew the Arado Ar68 in Czechoslovakia. But later he was assigned the Bf109, his favorite fighter. Throughout the war, he flew the B, C, D, E, F, and G models of this unique little fighter.
With 9./JG54 he flew his first combat missions in Poland and France as a Schwarmfuhrer. His first victory was a Gloster Gladiator. He was later given command of 7.Staffel. But on November 28th 1940, he commanded 9.Staffel, where he asked an unteroffizier of logistics who was a skilled artist, to create several ideas for a unit emblem. The one which Bob chose was the 'Devil's Head,' which was applied to every aircraft and unit vehicle. (After Bob left the unit, the 'Devil's Head' emblem disappeared)."