Vintage 18th c. marbled papers, Italian over Spanish moiré on Turkish Doubled marble pattern. From UW: “Though related, a Double marble is not the same process as an ‘Overprint’ (Wolfe plate XXXVII 180).
The first instance of Double marbling was seen in the 17th century. A Double marble is created when, after the first desired pattern is completed and the paper dried, the same paper is again treated with Alum and marbled with the second pattern over the top of the first. The primary colors for this example are yellow ochre and gold.” Scan of 2 d image in the public domain believed to be free to use without restriction in the US.