Trying to Identify My Lamp, Any Ideas?

I bought this at a government customs auction about 15 years ago and have not been able to find any information on it. I've not noticed any maker's marks or signatures, other than a stamped "51" on the top of the shade under the screw top with a sideways 5 and an upright 1 directly across from the "51".

The base and shade are both very heavy. I was told that it was an antique when I purchased it but don't have any other information. Any clues as to the artist, company, or value would be very appreciated.