A German medical document has proven an old urban legend true: Adolf Hitler only had one testicle.

German historian Peter Fleischmann has unearthed a long-lost prison medical record from Hitler’s incarceration after he attempted a coup in Munich in 1923. He was arrested and charged with treason over the affair.

The records showed that Hitler suffered from “right-side cryptorchidism” – in common parlance, an undescended right testicle.

Long considered by historians to be lost forever, the medical records surfaced at an auction in Bavaria in 2010. They were confiscated by the Bavarian government, and according to Reuters, have only recently been studied by Fleischmann, a professor at Erlanen-Nuremberg University.

Normally, tesicles descend from inside the body into the scrotum at some point during childhood. Fleischmann told the German newspaper Bild that one of Hitler’s testicles was “probably stunted”. Bild quoted him as saying, “The experienced medical officer [at the prison] immediately recognized the condition.”

Dr. Josef Steiner Brin, the medical officer at Landsberg prison, where Hitler was jailed, wrote in his report that the future Nazi leader was otherwise “healthy and strong.”

Speculation that Hitler was missing a testicle has existed for years, and the rumors even made their way into British pop culture by way of a song entitled “Hitler Has Only Got One Ball”. However, the generally accepted cause for his condition was a shrapnel injury from World War I’s Battle of the Somme.

The rumor was given credence when Franciszek Pawlar, a Polish priest and amateur historian, claimed that a German army medic who treated Hitler after the shrapnel incident had told him about the injury.

In addition to refuting that story, the medical records also contradict Hitler’s childhood doctor, who told American interrogators in 1943 that the future dictator’s genitals were “completely normal.”