From Marteau

Gold coin issued all over Europe at different values and standards of finess. Inspired a production of siver coins of the same value often referred to as linkducatons

First Ducats were issued in 1284 by the Doge of Venice, Giovanni Dandolo (1280-1289), the coin then belonging into the category of Zecchinos. The original weight was 3.537 g, the inscription read: SIT TIBI XPE (= Christe) DATVS, QUEM TV REGIS ISTE DVCATVS (you, Christ, shall be given the dukedom over which you rule). The coin was historically extremely stable – it was only slightly reduced in its weight to 3.49 g in 1526 and thus became the most important coin of trade in the Eastern Mediterranean whilst Hungarian ducats first minted after the design of the floren under Louis I (1342-1382) had begun to spread over central and northern Europe. The 15th century saw new Spanish ducats bearing the images of Ferdinand and Isabella (1476-1516) to celebrate the united kingdom of Aragón and Castile. Under archduke Ferdinand I (1521-1564) the ducat was declared the exclusive gold coin of Habsburg's territories. The Reichsmünzordnung of 1559 made the Reichs-Ducat of 3.49 g (986/1000 fineness) the main gold coin of the Empire. Scandinavia and Russia introduced a slighty less valuable ducat of 3.42 g after the model of the Dutch ducat of the same quality.

Ducats were usually accepted on the basis of their weight. The ratio agains silver coins had to established again and again following shifts in the instable gold/silver evaluation.

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