BBC paperwork states that this was originally titled as "The Cave of Five Hundred Eyes". When they came to recording, it had been shortened to just "Five Hundred Eyes".
The master videotape was wiped by the BBC in 1967. No footage is known to survive. However, director Waris Hussein passed a complete set of telesnaps to the BBC archives in 2004.
This episode takes place in China in 1289.
Telesnaps and extracts from the original soundtrack, are included as part of a 30-minute abridged reconstruction of the story "Marco Polo". This is included as part of "Doctor Who: The Beginning" DVD collection released in January 2006.
This episode was watched by 9.4 million viewers on its original transmission.