Consider that there is a two-sided cult relief found at Mithraeum I of Stockstadt (CIMRM 1162) simal to this in Dieburg (CIMRM 1247)
Lit. Ingeborg Huld-Zetsche/ Klaus Jürgen Rau (2001), Das doppelseitige Kultbild aus dem Mithräum I von Stockstadt, Saalburg Jahrbuch 51, 13-36.