Two and a half pints (over 1 litre) is large for a tankard but then again, much of North European culture revolves around getting drunk. After all, it is cold most of the year, there is not much sunshine and everyone is a little bit depressed half the time, so why not get peed?
Maybe the person who signed it had just drunk from it....
I can not make much (any) sense of the signature.
Lovely though, I am dirty green with tankard envy.
John.