This issue is a variant of Captain America (Marvel, 1968 series) #197 [25c price variant]. There exist further variants.
Letters page letter from Ralph Macchio.
Marvel Comics Index #8A lists letterer as Gaspar Saladino. Verpoorten credit by Nick Caputo,August 2012. Previous indexer credited Frank Giacoia.
in Capitaine America (Editions Héritage, 1970 series) #57 ([Mai 1976])
in Captain America & The Falcon: Madbomb (Marvel, 2004 series) #[nn] (2004)
in Marvel Gold: Capitán América: La Saga de la Bomba Loca (Panini España, 2011 series) #[nn] (Junio 2011)
in Captain America (Arédit-Artima, 1979 series) #18The Madbomb Part 5.
Letter from Ralph Macchio.
Marvel Value Stamp Series B #78 "Conan".