This research examines the silver and copper coins minted under Emir Isa ibn Muhammad ibn Abi Khalid al-Ma'muni (206-208AH/821-823AD) at the mints of Armenia during his governorship. The extant corpus of his coinage is limited to two denominations: dirhams and fulus. The study has classified four distinct types of dirhams struck at the Armenia mint, along with four additional types produced at the Arran mint. Furthermore, certain copper fulus bearing the date 208AH/ 830AD, whose mint location remains unspecified, have been identified and categorized into two distinct types. The significance of this numismatic investigation lies in its ability to compensate for the historical sources' inadequate coverage of al-Ma'muni's appointment, dismissal, and the events of his era. Consequently, this study employs the coins minted during his rule as primary evidence to illuminate historical events and information absent from traditional historical accounts. The research challenges stem from the paucity of historical sources addressing Armenia and its governors, highlighting the need for specialized academic studies in Islamic numismatics for this region. While Dr. Aram Vardanyan compiled a catalog of Islamic coins minted in Armenia “Islamic Coins Struck in Historic Armenia", his work was limited to deciphering select coin inscriptions, with some remaining unread, and lacked analytical examination of the numismatic evidence. This research focuses on analyzing the silver and copper coins issued by Emir Isa al-Ma'muni, which to our knowledge and based on available evidence, have not been previously studied or examined by scholars. Through systematic analysis of the dirhams and fulus minted at the Armenia and Arran mints, the study has yielded significant findings. Most notably, it establishes that the Emir governed Armenia in 206AH/ 821AD and 208AH/ 823AD information undocumented in historical sources, including al-Ya'qubi's works, which fail to record his appointment or dismissal. Furthermore, the research reveals the existence of a structured monetary system reflecting a degree of administrative autonomy in financial policies. As such, this study constitutes a novel scholarly contribution to the field of Islamic numismatics, particularly for this historically obscure period. It serves as a crucial primary source for understanding the political and economic contexts of the era, while simultaneously enriching Arabic academic literature in the domain of Islamic coinage studies. The study also corrected a rare silver dirham published by a researcher that was mistakenly attributed to Prince Issa al-Ma'mun. In light of the evidence, it was proven that the dirham was attributed to another prince. The numismatic evidence provides substantive documentation where textual sources are silent, offering new insights into the administrative and economic structures of Armenia under Abbasid rule.