|Out of Universe information|
The Giza coverstone is an artifact who was located in Giza, Egypt found by Professor Lanfgord and his team in 1928. Along with the Stargate, the coverstone was transported in the United States and stored inside the Cheyenne Mountain Complex.
The coverstone is formed by thirteen pieces forming a ring and a central round piece with a cartouche on it. Around the central stone is a warning written in Ancient Egyptian:
time million sky Ra sun god
coffin forever to eternity
door to heaven
A million years into the sky is Ra, sun god,
sealed and buried for all time
The cartouche is formed with six symbols inside it and a seventh one located at the bottom and part of it.
In 1928, Professor Langford's archeological team discovered the Giza coverstone (along with the Stargate). In 1939, all the material has been transfered from Egypt to the United States abord Achilles. It has been stored in the Cheyenne Mountain Complex where Professor Langford and Dr. Ernest Littlefield translated the cartouche and made experiments on the device. After Littlefield's accident in 1945, all the material, including the coverstone, has been stored inside an armory located at Washington D.C.. After 1969, Catherine Langford resumed her father's researchs and managed to transfer all the materials back inside the Cheyenne Mountain Complex. She hired Dr. Gary Meyers notably to translate the cartouche and try to find the secret behind the alien device (Stargate, Stargate: Continuum, SG1: "The Torment of Tantalus", "1969").
Daniel Jackson, who accepted Catherine Langford's job offer, arrives at the Cheyenne Mountain Complex and discovers the Giza coverstone inside a huge room. After the description of the writing on it told by Dr. Gary Meyers, Jackson fixes Meyer's translation on a black board to reveal the existence of a "Stargate".
Fifteen days later, Jackson explains his discovery and reveals the meaning of the symbols in the central cartouche. Those are constellations and are used to travel in the galaxies.