Monastery of Mantineion, 740-800. Seal (Lead, 24 mm, 13.81 g). Cruciform monogram MONHC within decorated circular border. Rev. MANTINЄ[I]OV within decorated circular border; in the centre, Greek cross within circle. A.-K. Wassiliou-Seibt: ὁ Χριστὸς αὐτὸς σφραγὶς ἀσφαλεστάτη - Byzantinische Bleisiegel aus der Sammlung Gert Boersema (forthcoming), 35. An extremely rare seal of an early Byzantine monastery and of great historical importance. Rough surfaces, otherwise, fine.

Ex Leu Web Auction 18, 19-21 December 2021, 4002 and previously from a European collection, formed before 2005.

Mantineion is the name of a town and an island in the Black Sea along the coast of Honorias, close to Claudiopolis (modern Bolu). By 740 at the latest, a double monastery was founded here by Saint Anthusa (700-755). Despite being vehemently opposed to the iconoclastic views of Constantine V, who even had her arrested and tortured, Anthusa gained the support of the empress Eudocia after predicting the birth of imperial twins. The empress made significant contributions to the Mantineion monastery. During its long history, the monastery seems to have had periods of exclusivity for either monks or nuns. The Mantineion monastery is also attested as a place of banishment for noble women in the 10th and 11th centuries.