Granat Brothers was a fine jewelry manufacturer, well known for die-struck high quality diamond mountings and wedding bands. They also ran retail operations in the San Francisco area. At some time-I think the early 1960s-Zales acquired their retail operations. Their manufacturing dies were acquired by another party. I have never seen a piece like you describe. It may have been a giveaway item in their store, or perhaps a piece of signage for the cases of retailers that sold Granat rings. My family handled Granat rings at their store in Pennsylvania, but I never saw any branded display pieces like that. It sounds small for a practical dish, and if flat I would assume a signage piece for a jewelry display. There is another contemporary jewelry operation in California, using the Granat Brothers name, and I have no idea of what connection, if any, it bears to the original manufacturer and retailer. Zales eventually phased the name out, renaming all their high end guild stores as Bailey, Banks and Biddle stores.