Also, if you look at the maps with the distribution of the sources of the timber it has areas of concentration that map quite closely to the southern remnants o

Also, if you look at the maps with the distribution of the sources of the timber it has areas of concentration that map quite closely to the southern remnants of the Hanseatic League (die Hansa in German) cities / trading stations. And some of the wood used has a time frame that sits right in the middle of the peak of the Hanseatic League power (1370-1438). The Dutch-Hanseatic War of 1438-1441 lead to the end of the Hanseatic League's de facto monopolisation of Baltic trade.