Copyright information was found in the Library of Congress online archive for this issue. The copyright date is listed as March 12th 1948. The cover date is listed as May 1948.
Silver Knight's appearance here follows his appearance in AMERICA’S BIGGEST COMICS BOOK #1. He appears next in WONDER COMICS #18.
Art revision from Lin Streeter to Oksner per Alter Ego #111 (July 2012).