First issue, spinning off from All-Star Western.
Part 2 of 2.
House ad for House of Mystery #203 (June 1972), advertised as "On Sale april 20".
House ad for House of Secrets #98 (June-July 1972), advertised as "On Sale April 6".
Next issue blurb (for #13), advertised as "on sale on or about June 1st".
Letters of comment from Bruce Long; Robert Ocque; Dan Gheno; Larry Morgan; Joe Arnold; and Mike Chestnut.