He is also known as the Golden Age or the 'original' Superman, who was finally killed off rather unceremoniously in Infinite Crisis, which I didn't care for too much.
This custom is not just a head swap to a JLU Superman body, its all been done from the ground up. The initial inspiration for this custom was the JLU  Metamorpho  head, which I thought looked a lot like an older Superman. Hair was sculpted on and then the head was put onto a JLU Atom Smasher body. The boots are sculpted, so are the ends of his sleeves just like in the comics. His distinctive 'S' emblem is hand painted. Styrene was used for the belt and the cape came from...well, you know, the other guy from Earth 1.