Here's the story as it unfolded in Green Lantern #43 (March, 1966) under this cover by Gil Kane and Murphy Anderson, in this story by Gardner Fox, Gil Kane and Sid Greene!
Catastrophic Crimes Of Major Disaster
Major Disaster sent the letters to Carol and Iris, to keep the heroes busy. Major Disaster wanted to remove their powers permanently, but could only switch Flash's aura with Green Lantern's ring charge. Green Lantern and Flash head back to Coast City, so Hal can charge his ring and they can check Hal's confidant, Thomas Kalmaku, and his casebook, in which he records all the details of Green Lantern's adventurers (including Barry's identity). Barry, after dusting for prints, finds two pair, Tom's and Paul Booker's.