I know this is a really old post but I happen to have the same thing described above. I have been told that it's a "handymans" job and someone cut the piece from an old lamp and made the rest. Maybe, but it seems odd that there would be another one just like it. (Or, this guy had the one that I now have)

I have posted some pics here if anyone is interested or could provide any additional information I would appreciate it.

Thanks,
John