This amazing thing! I purchased it from the same estate as the Santos I just listed, finding it wonderfully curious and very beautiful for all of its losses, and which a little research has taught me is a late 18th/early 19th century Italian Renaissance Revival marquetry panel, from the Lombardy region I believe, likely once part of a piece of furniture, probably with this narrative playing out over several panels. The white areas are etched bone; the gray and brown I believe are painted and etched hardwood; and there are a few small pieces of mother of pearl still inlaid as well—all adhered to a solid wood panel. Here's a link to example of a complete bench in this style, c. 1780. 

For me, it is the combination of what is present and what is absent that especially appeals to my sensibility, explicitly revealing its construction and also--as the scene seems to depict a return from war, with pieces of armor strewn on the ground and laurel wreaths in the hands of two of the women--evincing a sense of the toils of war and a hard won peace. 

20" x 14 5/8" x 1 1/4". Detail photos give a best sense of this, including the variety of materials and etched details, and also its losses, some leaving smooth surfaces underneath and others very rough. Now, it is stable and the panel itself sound and sturdy, wired on the back for hanging.