...an interesting discovery!

Imagine ! I discovered that this painting by Rembrandt is on a canvas with a pattern! 
Even more interesting for me is that the Wardens inspected the quality of dyed cloth. On the painting it looks like if they have a book with the samples before dying!
I made two close up screenshots and if I look closer to the'pages' in the book on the painting I get more and more convinced it is a book of textile samples...
I think I see the threads from the selvedges and the way the man holds the 'page' in the other picture may be of 'feeling' the page....
I will try to find more about it in the many publications about the painting!
www.labo.pt

Screenshots from original at 
https://www.rijksmuseum.nl/en/collection/SK-C-6

Info at the Rijksmuseum web page:
The Wardens of the Amsterdam Drapers’ Guild, Known as ‘The Syndics’, Rembrandt van Rijn, 1662

oil on canvas, h 191.5cm × w 279cm More details

The syndics inspected the quality of dyed cloth. Rembrandt portrayed them looking up from their work, as though disturbed by our arrival. This artistic device was a clever way of enlivening the scene and thereby involving the viewer. This late work by Rembrandt not only attests to his endless creativity, but also to his undiminished popularity among the citizens of Amsterdam.