Yes, the relics of the magi (aka "three kings") were, ahem, brought from Milan to Cologne in the 12th century. They were, or the pilgrimage to Cologne was, a major source of income or wealth for the city. The three crowns in the city's CoA refer to the magi. Interesting side note: While this territory was the arch-diocese of Cologne, the archbishop was not allowed to reside in Cologne. That was the result of a battle in 1288 which the archbishop lost. He was then forced to reside elsewhere (Bonn and Brühl became the bishops' residences), and Cologne became a free city. The archbishop even had to ask at the city border to be admitted into Cologne if he wanted to use "his" cathedral ... But in those days, the Cologne archbishop was an important office: Back then they were also rulers of a territory much like a king or duke, and the archbishop of Cologne was one of the prince electors, i.e. member of the body that elected the German king. Christian
Here is a much less impressive little albus struck by Archbishop Philipp II von Daun-Oberstein (1508-15) in 1511