The story behind the coin
January 1923: French and Belgian troops moved into the Ruhr to seize by force the reparations Germany was not paying. Berlin called for passive resistance and then paid the wages of millions of striking workers with money it simply printed. The mark, already sick, went into free fall. By autumn a single US dollar cost trillions of marks.
Coinage could not keep up, and everyone involved knew it. Metal money is slow — you cut dies, you strike blanks, you distribute. Paper can add a zero overnight. So the Reich's answer was mostly paper, and the coins that did appear were tokens chasing a number that had already run away from them.
Still, the mints worked. In 1922 they issued a 3 Mark in aluminium; in 1923 came the 200 Mark and, at the top of the ladder, the 500 Mark — the highest denomination the German Reich ever put on a struck coin. Aluminium was the obvious metal: light, cheap, and available, when silver and nickel had long since been melted for the war or hoarded by people who trusted metal more than promises.
This series is the pattern for that 500 Mark — a trial strike, a test piece made to check the dies, the alloy and the blank before mass production begins. Patterns are the mint thinking out loud. They are usually made in tiny numbers, rarely leave the building, and normally survive only because someone at the mint kept one.
The joke history played on it is exact. The Rentenmark arrived on 15 November 1923 and lopped twelve zeros off the currency; the aluminium 500 Mark was formally demonetised on 11 October 1924. A coin designed to be the biggest in German history was legal money for barely a year.

