Flag of Germany
When Heinrich XI, Prince Reuss of Greiz was appointed by Joseph II, Holy Roman Emperor to rule the then-new Principality of Reuss-Greiz on 12 May 1778, the flag adopted by the "Fürstentum Reuß-Greiz" was the first-ever appearance of the black-red-gold tricolour in its modern arrangement in any sovereign state within what today comprises Germany – the Reuss elder line that ruled the principality used a flag whose proportions were close to a "nearly square"-shape 4:5 hoist/fly ratio, instead of the modern German flag's 3:5 figure.
Symbols of the European Union
The flag was designed by Arsène Heitz and Paul M. G. Lévy in 1955 for the CoE as its symbol, and the CoE urged it to be adopted by other organisations. In 1985 the EU, which was then the European Economic Community (EEC), adopted it as its own flag (having had no flag of its own before) at the initiative of the European Parliament. The flag is not mentioned in the EU's treaties, its incorporation being dropped along with the European Constitution, but it is formally adopted in law.