Flax was used in the manufacture of ships sails which would have then been used in the shipyards of Stockton, in 1827 Stockton had four flax merchants and three linen factories.
The plaque read :-
This stone was erected to commemorate the completion of the 60th year of the reign of Queen Victoria. It was found near the village of Hartburn and used to beat flax on in former days.
A smaller much later plaque dates from 2nd April 1983, it shows the link between William of Hertburne, who became William of Wessyngton in 1183.
His descendant George Washington became the first president of the USA.