Seal from Artashat (Artaxata) with Parthian inscription of Mithra
Zhores Khachatryan proposes the following interpretation:
"N1021 (3 specimens): Parthian. (1) mtr > Mihr (or Miθr); (2) BYRT: fortress. In the documents on the Nisa ostraca, Mtrdtkrt BYRT = Mihrdātkirt diz "Mihrdātkirt Fortress" (V. A. Livshits). According to Livshits, in some documents, the abbreviated form Mtr appears instead of Mtrdtkrt. In other words, this is the seal of the Mihrdātkirt fortress, with which there was some official or commercial connection. "