The Delta 99 issue is the earliest printing identified to date. It might not be the original printing. Other printings include 5 x Infinito (Zig-Zag, 1970 series) #1, March 1970; Dracula (Buru Lan, 1972 series) #1, January 1972; 5 por Infinito (Baru Lan, 1974 series) #1, March 1974 [as Peligro en el Espacio]; 5 por Infinito (Ursus, 1981 series) #1, 1981? [as Primer Encuentro]; Zero Patrol (Continuity, 1984 series) #1, November 1984 [untitled]; Zero Patrol (Continuity, 1987 series) #1, [August] 1987 [untitled].
The Delta 99 issue is the earliest printing identified to date. It might not be the original printing. Other printings include 5 x Infinito (Zig-Zag, 1970 series) #2, April 1970; 5 x Infinito (Zig-Zag, 1970 series) #5, July 1970; Dracula (Buru Lan, 1972 series) #2, February 1972; 5 por Infinito (Baru Lan, 1974 series) #2, 1974 [as La leyenda de las sirenas]; 5 por Infinito (Ursus, 1981 series) #2, May 1981; Zero Patrol (Continuity, 1984 series) #2, February 1985 [Untitled]; Zero Patrol (Continuity, 1987 series) #2, November 1987 [Untitled].