The following information below was emailed to us from Peter Bower from London (a paper history and analysis expert):
"The watermark is a serpent devouring its own tail, the alchemical symbol Ourobouros¹. The countermark reads GMT the initials of the papermaker. Heawood records this mark in use in London during the 1720s and 1730s and says that this paper was imported from Genoa.
During this period English white paper making was just beginning to thrive but considerable amounts of fine white paper was still being imported from Holland and to a lesser extent from Italy. (Edward Heawood, “Paper used in England after 1600, part 2, 1680-1750”, Transactions of the Bibliographical Society, The Library, Second Series, Volume XI, March, 1931. Watermark 181 and notes on page 465.)"
SYMBOLS & WATERMARKS
A watermark is an identifying image or pattern in paper that appears as various shades of lightness/darkness when viewed by transmitted light (or when viewed by reflected light, atop a dark background), caused by thickness or density variations in the paper.²