The top opening is 2 5/8. The shade is in great shape for a 100 year old shade with 8 to 10 tight heat cracks and one chip on the bottom edge and has no glass lose on the inside of the shade.
That is shown on the last picture. I took many pictures which are part of the description. The item "Rare Whaley Leaded Lamp Shade, Stained Glass, Slag Glass, Arts Crafts, Handel Era" is in sale since Thursday, March 30, 2017. This item is in the category "Collectibles\Lamps, Lighting\Lamps\ Electric\Table Lamps". The seller is "bluegracymay" and is located in Kennewick, Washington.This item can be shipped to United States.