They can also be painted. I have also used them to front furniture. I was told they were made by Gucci or some other high end manufacture (cannot remember) but there are no markings and they are constructed out of what appears to be PVC.
I have owned them for about 20 years. Some are dirty some are clean. I have received several emails about the fasteners so I posted a pic of one or the original ones.
I have found that the new "Mechanical Fasteners" are much more low profile and come in a variety of finishes. Again, all available at your local hardware store. I have enough at this point to construct an 8 ft x 8 ft. The item "VINTAGE Mid Century Modern Architectural Panels" is in sale since Sunday, February 14, 2021.
This item is in the category "Antiques\Furniture\Other Antique Furniture". The seller is "giantrobota" and is located in Ann Arbor, Michigan. This item can be shipped to United States.