Just after independence Algeria knowns a lack in stamps, so many french stamps were over printed EA. There is two kind of surcharge "hand surchage" and "typographic surcharge".
yours is typographic surcharge.
As per Yvert catalogue :
HAND OVERPRINT
TYPOGRAPHIC OVERPRINT
your stamp is typographic overprint.
There was six bureaux which overprinted these stamps, a specialized catalogue list the mostly verieties of this surcharge.
these stamps are also listed in Scott & Michel catalogue
