This issue is a variant of Detective Comics (DC, 1937 series) #549 [Direct Sales]. There exist further variants.
On-sale date from DC Releases #11.
Color credits confirmed by Anthony Tollin.
Letters of comment from Elizabeth Holden, Stephen Scott Beau Smith, Dennis Payne, T. M. Maple, Rachelle Varia, Christopher Mortika, Mike Souza, Eric Tschler, Joseph Piergross and Scott E. Sears.