1930s (?) green star lamp

Can anyone help me identify or learn more about this lamp? I can't find anything like it out there. I'm not interested in selling it and don't need an appraisal. I believe it was purchased in the 1930s, and originally it had a plastic cylinder that sat down over the bulb and would spin from the heat. The plastic had fish on it so when you put the shade on it looked like they were swimming around. That piece is no longer around, however.