Source: John Guillim, A Display Of Heraldry, published in 1679
This is an example of a wire watermark. It consists of lettering, which appears to be "PMA_DVIT". It is perhaps the name of the papermaker. this watermark is most often placed beneath the shield-like watermark that is shown in the previous example. It apparently was not attached to the other watermark because its orientation varies from one mark to another.
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