Antiquity officials immediately hailed the wooden sarcophagus, found at the bottom of a 50-metre shaft in Saqqara, 20km south of Cairo, as the best preserved of its kind in the world.
Guy Lecuyot, from the dozen-strong French team from the Louvre Museum in Paris, said he had spotted the finds side by side when he was trying to extricate other mummies.
"It was when I was extricating the mummies, which had been looted, that I found the head of the wooden sarcophagus and a gilt head that seemed intact, from the Ptolemaic era," he said.
Secretary general of Egypt's Supreme Council of Antiquities, Zahi Hawwas, was delighted with the wooden sarcophagus.
"I have found hundreds of mummies and I can say that it is the best conserved dating from this period," he said.
"This type of discovery happens two or three times a century," Jean-Pierre Adam, an architect from the French team, said.
Site of discovery: The necropolis
of Memphis, south of Cairo
"Here, the miracle is that, so close to the surface, we found areas that had already been dug, except these two tombs which remain intact," he added.
Researchers are now trying to date precisely the sarcophagi and determine to whom they belonged.
Late last year, officials said the French team had discovered 19 mummies, as well as wood and limestone sarcophagi, in a burial ground in Saqqara.
The items date from the Late Dynastic Period, or about 1000 years BC, and the Ptolemaic era, Hawwas said at the time.