Found on the wreck site of the Henrietta Marie, sank 1700
By 1700, when the Henrietta Marie sailed, most Africa traders focused on the exchange of European manufactured goods for captive people but, even at the height of the slave trade, goods such as ivory, spices, and gold were still considered a valuable addition to the cargo. Scales and scale weights were used to accurately gauge the amounts of goods being exchanged between the English crew and their African trading partners.
African merchants soon became accustomed to European weights and measures. English slave trader Thomas Phillips, traveling on the ship Hannibal in 1694, noted “On the Gold Coast they know our Troy weights as well as ourselves and have weights of their own, which they compare ours with.”
Two scale weights were found aboard the Henrietta Marie. Among the cargo that the crew would need to weigh would have been the glass beads and iron bars that they were exchanging not only for people but also for supplies of fresh food, elephant’s tusks, and spices.
These weights are of different sizes. One weighs ¼ pound (troy) and the other is almost exactly one pound. It is likely that there are part of a set and that there are others still on the wreck site, not yet discovered. Shaped as two thick lead discs, they both bear proof marks of their certification by official British agencies. The letters “WM” surmounted by a crown signifies the approval of the offices of King William III, a dagger is the mark of the City of London, and an angel holding scales is the mark of the Plumber’s Guild, which oversaw all matters in which lead was used (plumbum being the Latin name for lead).
On the back of the smaller weight is inscribed a faint “WD”. These are the initials of William Deacon, the Henrietta Marie's original captain and one of its owners, and the mark is a good indicator that the weight was his property.
 Phillips, Thomas (1732). A Journal of a Voyage Made in the Hannibal of London, Ann. 1693,1694, p.198