Stan Lee's first mention of a Marvel "no prize" is in this issue's letters page.
in The Incredible Hulk Special (Marvel, 1968 series) #3 (January 1971) [title page]
in I Fantastici Quattro (Editoriale Corno, 1971 series) #20 (28 Dicembre 1971)
in I Fantastici Quattro (Editoriale Corno, 1971 series) #20 (28 Dicembre 1971)
in Marvel Masterworks (Marvel, 1987 series) #13 ([September] 1990)
in Hulk Vs. Thing (Marvel, 1999 series) #[nn] (December 1999)
in Marvel Masterworks: The Fantastic Four (Marvel, 2003 series) #3 [Regular Edition] ([September] 2003)
in Fantastic Four Omnibus (Marvel, 2005 series) #1 (2005)
in Hulk vs. the Marvel Universe (Marvel, 2008 series) #[nn] ([June] 2008)
in Los 4 Fantásticos (Editora de Periódicos La Prensa S.C.L., 1962 series) #37Cover inks credit from Nick Caputo via the GCD Error List (11 December 2007); the original indexer credited George Roussos.
in Fantastic Four Annual (Marvel, 1963 series) #4 (November 1966)
in The Incredible Hulk Special (Marvel, 1968 series) #3 (January 1971) [title page only]
in I Fantastici Quattro (Editoriale Corno, 1971 series) #20 (28 Dicembre 1971)
in Marvel Treasury Special, Giant Superhero Holiday Grab-Bag (Marvel, 1974 series) #[nn] (1974)
in Marvel's Greatest Superhero Battles (Simon and Schuster, 1978 series) #[nn] (1978)
in The Marvel Saga (Marvel, 1985 series) #13 (December 1986) [excerpt]
in Marvel Masterworks (Marvel, 1987 series) #13 ([September] 1990)
in Hulk Vs. Thing (Marvel, 1999 series) #[nn] (December 1999)
in Marvel Masterworks: The Fantastic Four (Marvel, 2003 series) #3 [Regular Edition] ([September] 2003)
in Fantastic Four Omnibus (Marvel, 2005 series) #1 (2005)
in Hulk vs. the Marvel Universe (Marvel, 2008 series) #[nn] ([June] 2008)Letters of comment from John Davidson; Owen Boylan; Alan Backer; Lane Hartman; Derrill Rothermich; Joey Polozola; Don Milliken; Allen Haworth; Dannie Brown; Reed J. Keonte*; Tom Jones; Bruce Solof; and Dave Oyerly. (* In his reply here, Stan writes, "And, as usual, we'll award no prizes! If there are no winners, then no one can LOSE!")