The SS-Totenkopfverbände (Death's Head Units): This specific branch of the SS wore the skull on their right collar tab. They were responsible for building, organizing, and administering the Nazi concentration and extermination camps
The Totenkopf (German for "death's head" or skull) was a universal cap badge and insignia of the Nazi SS (Schutzstaffel). To the SS, it symbolized fanatical loyalty to Adolf Hitler, contempt for death, and an absolute willingness to commit acts of terror and violence in the name of the Nazi regime