I think there was tin related trade between Cornwall and Brittany.
A lot of the copper that was combined with the European/Cornwall tin apparently came from the Great Lakes area in North America. All ancient copper ingots and bronze are traceable to their origins by the impurities. Most of the copper in ancient Europe is “untraceable” except that it has been traced to North America which is unacceptable. Don’t ask me for citations. It’s been along time. It is on the web somewhere and in books. Barry Fell wrote about it.