Very rare cancel on the "Aigle" issue you have.
The cancel on your stamp has a partial double imprint.
The first post office in Assenie oped in 1863.Although 30 years prior mail was going through Assenie.
Only 4 values of the"Aigle" issues were used in Assenie.
The 10c,20c and from 1865 the 20c & 80c.
In conjonction to the lozenge ASI cancel you had markings on covers
like ""Etablissement de la Cote d'or Assenie" and from 1865:"Cote d'or et Gabon-Assenie".
In 1871 there was a diminuation of service.From 1887 cancel type "Assenie-Gabon" appeared.Then in 1890 "Grand-Bassam-Senegal" &
In 1890 "Cote d'or en Afrique" & then in final "Cote d'Ivoire- Assenie".
This pic below from e bay. ACI on a general colonies Napoleon(1871) issue.Given the rarety of this cancel ,pics are rare to !
Of coarse it woud be nice to be able to compare with a dozen others but it is a hundred times rarer than Reunion or Martinique or even Gabon lozenge cancels.......