This issue is a variant of Action Comics (DC, 1938 series) #664 [Direct].
1991 Triangle #12.
Story continued from ADVENTURES OF SUPERMAN (DC, 1987 series) #477 and story continues in SUPERMAN (DC, 1987 series) #55. Chronos was stuck in the past in BLUE BEETLE (DC, 1987 series) #22.
Letters from readers - Kevin J. Conley, Charlie Harris, Ali T. Kokmen, Justin Pollack, Eric Skudlarczyk, Michal Jacot, Jerry Smith and Randy Keefe - and responses from Dan Thorsland.