Source: C. Suetonii, Tranquilli Opera Omnia, published in 1684
This is an example of a wire watermark. The four images which are presented on this page display a wreath-like shape surrounding a triangle of simple one-line discs. The first two images display two slightly-different 'bottoms' of the wreath shape, while the last two images display the opposite side of the wreath. The watermarks in all cases are located at the binding edge, thereby making it very difficult to take good photographs, but the two disc shapes are clearly seen in the watermark.
Additional Book Information
C. Suetonii Tranquilli Opera Omnia, Que Extant. Interpretatione, Et Notis Illustravit Augustinus Babelonius, Jussu Christianissimi Regis Ad Usum Serenissimi Delphini. (Published at) Parisiis: Apud Andream Pralard, Bibliopolam, via Jacoaea, ad insigne Occasionis. Cum Privilegio Regis. 1684