This was a battle in northern Germany not far from Danzig.
Any copper would have been from European sources. Some Tin was found. Might have been from Wales or The alps.
https://www.sciencemag.org/news/2016/03/slaughter-bridge-uncovering-colossal-bronze-age-battle
https://en.wikipedia.org/wiki/Tollense_valley_battlefield
Then who took the missing 230,000 tons of pure copper during the height of the Bronze Age? There is more than ample evidence that people went between NA, Europe, and Near East in those times