In this paper there are presented results of applying the methods of the time series analysis to the problem of recognizing small boats. It has been showed that the acoustic signals of the boats can be classified by means of clustering algorithms.

The subject of the discussion is the attribution of the Friedensburg 648 (283), 649 (280), 650 (282) hellers with the representation of Virgin Mary with the Christ child and the eagle of Lower Silesia. The coin was found during archaeological works conducted in 1999/2000 in Tarnów Jezierny. The find was crucial for determining that the coin was struck before 1442. The location of its coinage - Głogów or Lubin is still a matter of discussion.