(Surcharge because of the devaluation of the Spanish Currency)Translation:
Sage stamps from France were used in Morocco until 1890 before being surcharged in Spanish currency (centimos and pesetas) for commissioning on 1 January 1891.
Indeed, the depreciation of this currency and the speculation that had developed through the purchase of large quantities of stamps in Tangier, during the peseta, and resold in France, during the franc, led the administration to create special stamps only in Moroccan offices. Thus, three first values #8203;#8203;were put into action on January 1, 1891 (25/25 c, 50/50 c and 1 peseta / 1 franc) followed by three other values #8203;#8203;on January 1, 1893 (5/5 c, 10/10 c and 20/20 c). Thereafter, a value of 2 pesetas / 2 franss completed these emissions, to which was added a yellow 5/5 c, which explains why this series has eight values #8203;#8203;(Yv 1/8).
To date: • thirteen French values #8203;#8203;are known on letters ranging from 1 ct to 1 franc, to which must be added five values #8203;#8203;listed in different catalogs * and studies ** not yet seen on documents; • no parts were seen in the U.P.U. from January 1st, 1876, • all the pieces object of this presentation are in the tariff U.P.U. May 1st, 1878.
After the issue of overprinted stamps, French stamps without surcharges could be used by those who possessed them and this tolerance continued until at least 1913 when this use was prohibited, except for military correspondence, following the creation of the Moroccan Postal Office resulting from the merger of the French posts and the Cherifian posts **.
http://www.academiedephilatelie.fr/...mah_1501.pdf