Inside the alien's cave can be seen numerous props from Voyage to the Bottom of the Sea (1964) including the Seaview's navigation chart and missile silos.
The wall where Doug & Tony are strapped when the Extractor probe is used on their minds is very similar to the interrogation area with the computers where Major Don West is restrained in #3.1 of Lost In Space.
This episode takes place near Khartoum, Sudan on November 2, 1883 and in Arizona in 1968.
In 1968, this episode was nominated for an Emmy for best cinematography ( Winton C. Hoch), but lost to Ralph Woolsey for It Takes a Thief.
This is production number 9629.