The Pottmütze is the traditional headgear of the fisherman farmers from Mönchgut on the island of Rügen and was widely worn until the mid-19th century.
Only two caps from that time were found in local museums:
this one in the Heimatmuseum Göhren and another cap in the Stralsund Museum. The latter is worked with plantdyed yarn, shows five colours and was published in the Piecework Magazine, Fall 2020.

The Pottmütze is a stocking cap like many caps in the northern hemisphere, knitted either with colours (black and white, natural sheep wool, Pommeranian Coarse Sheep), or with 5 colours (natural dyed sheep yarn), which you can see here.

The best yarn for this cap is natural wool, 100%, no super-wash. If you are sensible to coarse wool, you can knit the inner brim with a softer yarn in the same yarn weight.
The main pattern is for adult heads, but a PDF with charts for 3 sizes (large, medium, small) is available for download as well.