This pocket watch was used to contain Hitler's soul.
When Adolf Hitler contemplated suicide in order to avoid capture by the Soviets, Commandant Nauhaus convinced him to seek out another way to survive. Using knowledge from The Thule Society, Nauhaus was able to place Hitler's soul inside a golden pocket watch. It was intended to be transferred elsewhere for safe keeping, but the Soviets managed to get their hands on it by killing the Thules who were transporting it.
The watch would end up with a Russian family, before moving to China and Peru, before eventually arriving in Columbus, Ohio in 2016, where the Thules would finally locate it.
With the pocket watch finally in their possession, The Thules began a plan to resurrect the Führer. They tracked down a descendant of his, Ellie Grant, and used her blood in a ritual to bring back the Führer, with Nauhaus acting as a vessel.
The ritual was a success, and Hitler came back, however, years spent inside the pocket watch seems to have messed up his mental state. The Winchester brothers also arrived to try and stop them, and succeeded when Dean Winchester shot the Führer in the head, killing him.
The pocket watch itself made from pure gold. According to Marv the antique shop owner, it was made in 1931 by an unnamed manufacturer which no longer again produced it. However, The Thule somehow modified it, adding various advanced mechanisms in order to hold someone's soul and perform advanced spellcasting like the Das Blut.
- Christoph described the pocket watch as a Horcrux, which is a name for any object in the Harry Potter series used to hide a piece of one's soul. In Harry Potter, chasing down the Horcruxes was a major part of Harry Potter and the Deathly Hallows as destroying them was the only way to kill the main enemy, Lord Voldemort.