Craig Delich and Pat Lang say Jim Mooney pencilled this cover. Bob Klein, Gene Reed, Mike Tiefenbacher, and Bob Hughes say it was Dick Dillin.
Letters credit from Todd Klein via his Klein Letters blog (18 September 2016, http://kleinletters.com/Blog/ira-schnapp-in-worlds-finest-comics-part-1/).
Klein/Reed say Kelsey inks. Craig Delich and Pat Lang say Moldoff 2/05
Writer credit from Showcase Presents Green Arrow #1.
Avg Circ: 480,000
Publisher:National Periodical Publications, Inc.
Editor: Jack Schiff
Owners: H. Donenfeld,I. Donenfeld, S. Iger, H. Donenfeld Foundation, J. Liebowitz, P. Sampliner, S. Sampliner
575 Lexington Ave, NY, NY