12th - 14th Century A.D. Medieval Byzantine trachy "cup" coin. 20-28 mm diameter. 2.82 gram weight.    Trachy or "cup" coins are odd shaped coins looking like they could have been formed by taking a normal coin & pushing a thumb into the center of the coin. Stuck during the 11th-14th centuries, no one is certain why they were made in this shape, but most likely to reduce counterfeiting. Many of these coins are made of a mixture of copper and billon ( a debased silver, sometimes about 20% ) but most of the time the amount of silver was so small the coins would mainly appear as copper or bronze. Because of their shape, the picture inside the bowl gets less wear than the outside design. Many of these coins depict Christ wearing a halo (nimbate) on the outside, or sometimes Mother Mary. The inside usually had a depiction of the Emperor often with his Empress.