Large gold and cornelian seal ring. Southern Italy. 13th century.

Large gold and cornelian seal ring. Southern Italy. 13th century.
 
Unusual ring formed by a large round, mounted stone which depicts a knight on his steed, carrying a sword and a shield.  
The Aquinas family’s coat of arms, with a gilded background with diagonal red stripes, is engraved on the shield. This is the seal of Count Thomas Aquinas, count of the city of Acerra, in the Naples region, and paternal uncle of Saint Thomas. He was the right hand of Frederick II, the Holy Roman Emperor and the Count of Aquinas led the Seventh Crusade to the Holy Land in his name.  
Around the stone the ring bears the inscription + S- THOMAE-DE- AQVINO and engraved inside is the word "Fideliter" ("The most faithful")
This is most certainly an authentic ring, a gift from King Frederick II of Sicily to his right-hand man, the count of Acerra. 
The part made of gold displays the style of goldsmithing of Frederick II with two stylised palms which hold the stone. This is typical iconography of 13th century art in the south of Italy, in the emperor’s court.  
Bibliography: •Catalogus Baronum. Commentario, editor: E. Cuozzo, Rome 1984, §§ 1008, 1009, 836. 
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italiane, Naples 1905-1909; 
•F. Schneider, Toscanische Studien, in "Quellen und Forschungen aus 
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Jérusalem, III, Paris 1936, pp.276, 286, 302-304, 400; 
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"Mélanges de l'École Française de Rome", 106, 1994, pp.653–665; 
•E. Cuozzo, La nobiltà dell'Italia meridionale e gli Hohenstaufen,  
Salerno 1995, pp.29 ss., 94 ss. 
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federiciana, Vol. 2,Instituto dell'Enciclopedia italiana Treccani 
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, 1875 e 1882. 
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non comprese ne' Seggi di Napoli, imparentate colla Casa della 
Marra, Naples 1641. 
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Regno di Napoli, Naples, 1717. 
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généalogiques et historiques des Princes du Royaume de Naples 
affectionnés a la Couronne de France, Paris, 1663. 
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Florence, 1580.