This is a beautiful, true vintage shade that is real stained and leaded glass with a copper mounting cap. It looks like one of the tiles on the bottom is cracked (see photo with arrow).
I can find no other notable issues with the shade. You may want to clean it further. Measures just over 13 W. The hole diameter is 1 5/8.
The item "Vintage Round Purple Tiffany Style Stained Leaded Slag Glass Lamp Shade 13.5" is in sale since Monday, January 27, 2020. This item is in the category "Collectibles\Lamps, Lighting\Shades". The seller is "bijouhills" and is located in Saint Petersburg, Florida. This item can be shipped to United States, United Kingdom, Denmark, Romania, Slovakia, Bulgaria, Czech republic, Finland, Hungary, Latvia, Lithuania, Malta, Estonia, Australia, Greece, Portugal, Cyprus, Slovenia, Japan, China, Sweden, South Korea, Indonesia, Taiwan, Thailand, Belgium, France, Hong Kong, Ireland, Netherlands, Poland, Spain, Italy, Germany, Austria, Bahamas, Israel, Mexico, New Zealand, Philippines, Singapore, Switzerland, Norway, Saudi arabia, United arab emirates, Qatar, Kuwait, Bahrain, Croatia, Malaysia, Chile, Costa rica, Dominican republic, Panama, Trinidad and tobago, Guatemala, Honduras, Jamaica, Aruba, Belize, Dominica, Grenada, Saint kitts and nevis, Turks and caicos islands, Bangladesh, Brunei darussalam, Bolivia, Egypt, French guiana, Guernsey, Gibraltar, Guadeloupe, Iceland, Jersey, Jordan, Cambodia, Liechtenstein, Luxembourg, Monaco, Macao, Martinique, Nicaragua, Pakistan, Paraguay, Uruguay, Russian federation, Canada, South africa, Colombia, Antigua and barbuda, Saint lucia, Barbados, Bermuda, Cayman islands, Sri lanka, Maldives, Oman, Reunion.