It is not marked but most likely a Rainaud or A&R, Newark, NJ. Condition is excellent, with some minor paint flaking & pencil marks to the base.
Please view all pictures provided as they are the best description. The item "Antique Arts and Crafts Slag Glass Lamp with Pottery Base Rainaud" is in sale since Tuesday, August 7, 2018. This item is in the category "Antiques\Decorative Arts\Lamps". The seller is "tewks123" and is located in Rock Tavern, New York. This item can be shipped to United States.