In the Middle Ages, the German Empire was not a uniform currency area. But in 1354, the archbishops of Cologne, Mainz and Trevere agreed to henceforth issue their gold coins at the same values. The Cologne gulden that was created by this treaty was widely disseminated and became a forerunner of the later Rhenish Monetary Union. Its obverse bore the crest of the minting archbishopric, while the reverse depicted Saint Peter.