A very rare variety of the Wrymouth denarius.
The denarius of the "bishop and knight" type is known from two basic varieties, differing in the reverse. The first, more popular, with a single name (of Saint Adalbert) in the rim. The second is much rarer, of which this piece is a representative, with two names (of the prince and the saint).
The variety has been difficult to obtain for years now, as Stronczynski, for example, wrote about at the end of the 19th century.