These stamps were issued in 1966, overprinted "Centenaire du Timbre Caire 1966". They depict the submerged Nile sphinxes at Wadi es Sebua and a colossal statue of Queen Nefertari.
The original stamps were part of a set of 6 issued in 1964 for the UNESCO Campaign.
Were these two stamps the only ones reissued with an overprint in 1966? If you know, do add a comment :¬)