At this the duke [Géza] was greatly annoyed.According to the 14th-century Illuminated Chronicle, Franco served as a bishop of one of the dioceses of the Kingdom of Hungary and was considered a loyal confidant and councilor of King Solomon by 1071.
His name appears in Géza's establishing charter, alongside archbishops Nehemiah of Esztergom, Desiderius of Kalocsa and suffragans Aaron, Gecticus and Lazarus.
[4] In contrast, Péter Váczy identified Franco's (titular) episcopal see with Belgrade (today Serbia's capital), where a Greek-ryte metropolitanate located at the turn of the 11–12th centuries.
[4] There is another source, the death register (obitury) of the Saint Lambert's Cathedral, also in Liège, which commemorates a certain deceased Franco, the bishop of Veszprém ("commemoratio Franconis episcopi apud Vesperem que est civitas Hungariae"), who died in 1081.
Székely identified his person with the Polish prelate Franko ("episcopus Poloniensis"), who was a councilor of Władysław I Herman in the 1080s, according to the Gesta principum Polonorum.
He visited the Abbey of Saint-Hubert in this capacity in 1081 during the consecration of the new altar dedicated to Saint Giles, in the companion of Henry of Verdun, the bishop of Liège.