CREATE TABLE table_38310 ("Start month" TEXT, "End month" TEXT, "Cover" TEXT, "Spine" TEXT, "Indicia" TEXT, "Masthead" TEXT, "Number of issues" FLOAT)

Which spine has 12 issues?
SELECT "Spine" FROM table_38310 WHERE "Number of issues" = '12'
SELECT "Spine" FROM "table_38310" WHERE "Number of issues" = '12'