In 1304 the introduction of the "basilikon", a pure silver coinage modeled on the Venetian ducat marked the abandonment of Komnenian structures under the influence of western models. The system that began in 1367 was constructed around the "stavraton", a heavy silver, equivalent to twice the weight of fine metal of the last "hyperpyra". By the end of the 12th century, especially from 1204 on, the political fragmentation of the empire resulted in the creation of coinages that were either "national" (e.g. in Trebizond in 1222, in Bulgaria in 1218, and in Serbia in 1228), colonial or feudal. Venetian coins soon penetrated the monetary circulation in Byzantium. This situation stands in contrast with the monopoly that Byzantine currency had enjoyed until the 12th century, within its own frontiers, and through its diffusion in the lands beyond — a measure of its political and economic influence.