I discovered the artefact in these photos in 2018 while diving on the Mullion ‘Pin Wreck’, a mid-17th century merchantman wrecked off the west coast of the Lizard peninsula in Cornwall, England. It is a two-pound Amsterdam blokgewicht (block weight), a type of copper-alloy weight shaped like a truncated cone that was used by Dutch merchants from the 17th to the 19th century (Nagel 2013, 2019; van Diest 2016, 2019). 17th century examples are rarely found, and this is one of the oldest known …