P3X-298
From The Stargate Omnipedia
Planet Daniel Jackson (and perhaps SG-1) traveled to, where he collected a mass fragment. He returned it to the S.G.C. for a carbon dating analysis. It had been covered in the domestic, pre-dynastic period of Egypt.
KEY EPISODE
Heroes, Part 1 - Dr. Jackson recieves a fax regarding the mass fragment from P3X-298.