What is the name of the primary symbol, which is now outlawed outside of the context of art or science, and was widely used even on the state flag?
Strafgesetzbuch section 86a The German "Strafgesetzbuch" (Criminal Code) in § 86a outlaws "use of symbols of unconstitutional organizations" outside of the contexts of "art or science, research or teaching". This concerns Nazi symbolism in particular and is part of the denazification efforts following the fall of the Third Reich.
Flag of Delaware The flag of the state of Delaware consists of a buff-colored diamond on a field of colonial blue, with the coat of arms of the state of Delaware inside the diamond. Below the diamond, the date December 7, 1787, declares the day on which Delaware became the first state to ratify the United States Constitution. The colors of the flag reflect the colors of the uniform of General George Washington.