Over 16,000 watermarks from books printed between 1450 and 1501 in the Low Countries (today the Netherlands and Belgium).
The Koninklijke Bibliotheek offers access to 16,071 watermarks from books printed between 1450 and 1501 (incunabula) in the Low Countries (today the Netherlands and Belgium) in the Watermarks in Incunabula printed in the Low Countries (WILC) dataset.
The WILC set comprises 16,071 illustrations of watermarks taken from the 2,229 incunabula editions preserved in 14,300 copies worldwide (many of them in more than one copy). The set includes watermarks from books held in libraries, archives and museums all over the world.
The KB offers this as open cultural data: there is a CC0 licence for the metadata, there is also a CC0 licence for the individual objects (illustrations of watermarks).