This metal lamp shade is marked PATENTED NOV 10 1908.  I did not find a maker's mark. It is one-piece and a magnet does not stick to it. I suspect it to be brass or bronze. All patina is original and it's speckled with paint, verdigris, and a few scratches. It has held its shape well, with a small area of bumpiness. 

I've not cleaned it but you may do so if you wish. The measurements are: 5 3/4" wide x 6 1/4" long x 3" tall x 18" around. It weighs 3 ounces and will ship free via USPS to the lower 48 states please.