Another issue of Compelling magazine (I've decided to bump the timeline back by three years and will have to tweak the dates on issues done so far).
From September 1953, the first part of "The Way Of The Tyrant" about future dictator Colonel Green. The story contains a throwaway line about Khan Singh from "Last Days Of The Supermen" and it was here that Roddenberry had the first inkling of creating a future history.
Edit: Working late on little sleep is good for creativity...bad for spelling. Will have to fix Isaac's name. Goddamitsomuch!