As explained elsewhere, E.A. stands for "Etat Algerien". These overprints are the first issues from independent Algeria, right after the 1962 referendum. Because France did not want to give the impression it was planning to lose the independence vote (although the writing on the wall was plain for all to see), local post-offices were allowed to stock up on these 5 issues, the 10c and 25c definitives, and three commemoratives issued previously by France but that showed Algerian scenery. But the printing of new Algerian stamps in advance was not done. So after the vote took place, each post-office scrambled to create an EA stamp, sometimes also taking care of blacking out the "Republique Francaise" inscription, but not always, until the new Algerian state could get its act together and distribute standardized overprint stamps. So, in theory, we have as many hand stamps types as there were post-offices, although they are all catalogued under the same numbers YT#354-358. A veritable zoology of those exist, with inverted and multiple overprints, with and without bars, etc... The typographed overprints that came afterwards are catalogued as YT#359-363.
On the top two rows, the standard overprint issues. On the bottom row, my samples of the hand-stamped issues.