Antique Lamp...of unknown origin

I just inherited this from my grandmother's house -- I recall seeing it there for 40 years. My dad says that it was an antique when it was gifted to her from her mother-in-law. Thus -- I'm thinking it's maybe 80 or 90 years old. I can't find any markings on the lamp to indicate who made it. It works. No plastic or refurbishing -- that I can see. Any idea what it is?