My Grandmothers Antique Slag Glass chandelier

I have loved this chandelier since I was a young child, 50 plus years. It has been passed down to me and I am thrilled to have it! I have no history on it other then it was given to my grandmother from someone in New York. I am hoping someone out there can tell me something about it. I would like to know how old it is and who it was made by. Also I'm curious if it has any value. Any info would be greatly appreciated. Thanks