According to Schaffenberger in a 1998 letter, many covers at ACG were penciled and inked by him, but signed by Pete Costanza because DC editor Mort Weisinger (for whom Schaffenberger worked on the Superman Family titles at that time) did not want him drawing superhero covers for other companies.
house ad for Herbie (American Comics Group, 1964 series)
Letters submitted by Dan Noon; Dale R. Gowin; Danny Doyle; Mark Savage; Larry Herndon
Everson pseudonym noted in Jerry Bails's Who's Who in American Comic Books