Source: Andreas Morellius, Specimen Universae Rei Nummariae Antiquae, published in 1683
This is an example of a wire watermark, depicting the letters "C" and "S" on either sides of a heart, all inside a rectangle.
Additional Book Information
Specimen Universae Rei Nummariae Antiquae, Quod Literatorum Reipublicae Proponit Andreas Morellius Helvetus. (Published at) Parisiis: Apud Thomam Moette, via vulgo dicta de la Bouclerie, juxta Pontem Sancti Michaelis. Cum Permissu. 1683
