Polish coinage of the late 12th century remains an unsolved mystery in many ways. Written sources and archaeological evidence for this period were scarce until the discovery in October 1987 in Głogów of one of the largest hoards in Poland and Europe. The hoard comprises nearly 23,000 small silver deniers and fragments. The earliest coins are issues of German margraves and bishops from the 11th/12th century. Then there are coins of the Polish duke Boleslaus III the Wrymouth (1102-1138) and his sons, from the early phase of the feudal fragmentation. These have a reliably substantiated attribution and chronology. The latest group are a few types of denier, counted in hundreds and thousands. Their attribution is very problematic — a possible source is Silesia, part of Poland. The study of this group of coins can shed new light on at least a part of the mystery of late 12th-century Polish coinage.