Amidst the carnage of destruction on site 35F was a remarkable discovery from the northeastern (stern) end of the wreck: An intact one-foot arm of a two-foot wooden folding rule, an early form of ‘pocket calculator’ incorporating five scales used to measure the areas and volumes of timber. The artifact was subsequently conserved at the York Archaeological Trust and its use and significance documented.

Relying on the English inch, this extraordinary find reveals the nationality of the ship’s crew to have been English sailors of the second half of the 17th century. The wooden rule is the earliest known example ever found on any shipwreck in the world. Significantly, this seemingly simple and crude device provides a rare glimpse of the mathematical skills and competences performed in the working life of early modern England.

 A description of this unique one-foot long artifact is further outlined below:

• In addition to its five different scales, a separate table located at the foot of one side functioned as a primitive mathematical ‘calculator’ to assess the cubic content of timber.

• Incised graduation marks from three different scales extend vertically along the other side of the rule. The external, outer master scale consisting of 12 inches marked by lines graphically and numerically, progresses in ascending order from the base upwards towards the hinge. These inches are subdivided through vertical incisions into 1/2, 1/4 and 1/8 inch.

• A further 12 inches, marked 13-24, would have continued along the corresponding lost arm, creating a two foot-long carpenter’s rule.

• Two bronze pins protrude perpendicular out of the interior edge and a wooden hinge with a bronze pin would originally have folded the two arms together.