Picked up this tablespoon in a little job lot the other day.
The incuse duty mark was used from 1st Dec 1784 until 28 May 1786.
According to Gill, it seems there were seven silversmiths who sent silver in for assay to Newcastle in that period.
Samuel Thompson II (a small amount)
Francis Solomon (a VERY small amount)
Langlands & Robertson (by far the largest sender)
Pinkney & Scott
This example is from the Pinkney & Scott Partnership. (Maybe someone should try and collect an example of each of them! :) ).