Hi John,
I tend to agree. This does not look like any socket hardware that I have encountered on early lamps. For on thing, there is no integrated switch mechanism and it looks like it was meant for a hardwired fixture (ceiling lamp, sconce, stair case globe, etc.). Too early for a in-cord switch. It only makes sense that, to function as a lamp, it would require a switch. I do not know how far back wall switch control was common on electrical outlets but that would be the only other alternative. Unless.... the socket was replaced at sometime with the one you have now?
In good light (and close up) the darker amber swirls of the glass seem to have a opal-esque quality which I have never seen before in glass. It is stunning in sunlight. Does your lamp exhibit similar qualities?
Best Regards,
Bill