The history of Earth-40 prior to 194o is largely unknown.  Vandal Savage is known to existed for millennia in this timeline, much as he has in others, but the details of his history are unexplored. In the 19th century or perhaps earlier, an organization known as Skeleton began to operate globally, dealing with unusual existential threats.  The operating through a series of agents known as the Whistling Skulls.  Seven Whistling Skulls are known to have acted in the behalf of Skeleton, most of whom have never been identified.  Skeleton employed a number of unusual operatives and had access to technology and materials far advanced from what was generally known.   The 6th Skull was John Singleton, who assumed the role in 1918 operating during World War I up until 1940, when he was believed killed on a case in Japan. 

In London in 1925, a boy name William Massey met Nigel Singleton, son of the 6th Skull and started a series of events that led him to assuming the role himself.  Over the next 15 years, the 6th Skull watched Massey grow and was impressed with his physical agility and cunning as a paper boy and low level bandit of apple carts and grocers.  Overtime, Massey became more systematic, organizing paper boys under his leadership and become more affluent and reputable.  He also maintained his friendship with Nigel Singleton, a simple-minded youth with physical strength bordering on the super-human.  Concerned for his son, John Singleton providing him with a lotion that hardened his skin, protecting him from physical injury and the effects of his own strength.  At Singleton's direction, Massey was groomed to the 7th Skull should he ever be needed.

In 1940, Skeleton worked with the Justice Society on a case in Japan involving giant robots of incredible power.  In a pitched battle, the 6th Skull along with The Clock, the Owl and the Cat were overwhelmed, resulting in the deaths of the Cat and presumably the 6th Skull.   Massey was offered and accepted the role of the 7th Skull and Nigel adopted the identity of "Knuckles", the Skull's sidekick and Man Friday.

The first case on the new Skull occurred in Switzerland, where a remote village had experienced a series of bizarre disappearances.  Upon investigation, The Skull and Knuckles discovered that the villagers had been harvested by Klaus Hellman, a Nazi scientist attempting to create monsters in the service of the Reich.  Most of his experiments failed, leading him to be cast out of Berlin but enough succeeded to create a Karneval of freaks and monstrosities that he used as a cover for his operations.  After some initial setbacks, the Whistling Skull, Knuckles and the townspeople turned the tide and Hellman was captured.  Massey and Singleton returned to their civilian identities in London where the met with Clock and Owl, who restored some of the equipment they had lost in Switzerland and implied an offer, presumably membership in the Society.  Hellman was intercepted by the Nazis though his fate is unknown and the further adventures of the 7th Whistling Skull, including the potential survival of the 6th, have not bee recorded.(Liberty Files: The Whistling Skull LS).