This original 501-9 shade is the harder of the two 501 shades to find. It is quite easy to tell from the 501-11 shade since the paint in it's design is arched.
This original 501-9 shade was painted white then fired. There are reproductions which have "frosted" or etched glass, and are smaller in size. Some of the newest reproductions are quite close in resembling the original with fired white paint. Always count the panels on the shade as reproduction so far have only had 8 panels in the shade while the originals have 10. Some reproduction shades are marked with an oval signature on the inside.