John Guillim, A Display Of Heraldry, published in 1679
(Fifth example)

This is an example of a wire watermark. It appears to be neither an image of a known object nor a letter, but rather a unique symbol created to represent the papermaker.

Additional Book Information
A Display Of Heraldry: Manifesting A More Easie Access To The Knowledge Thereof Than Hath Been Hitherto Published By Any, Through The Benefit Of Method; Whereunto it is now reduced by the Study and Industry of John Guillim, Late Pursuivant at ARMS. The fifth edition much enlarged with great variety of BEARINGS. To which is added a TREATISE OF HONOUR MILITARY AND CIVIL, According to the Laws and Customs of England, collected out of the most Authentick Authors, both Ancient and Modern, by Capt. John Logan. Illustrated with variety of SCULPTURES sutable to the several Subjects; to which is added a Gatalogue of the Atchievements of the NOBILITY of England, with divers of the GENTRY, for Examples of BEARINGS. (Published at) London: Printed by S. Roycroft for R. Blome; and are sold by Francis Tyton, Henry Brome, Thomas Basset, Richard Chiswell, John Wright, and Thomas Sawbridge. 1679