Before the days of the wall outlet that we use today, electrical appliances where connected to your house wiring by a plug that screwed into a lightbulb socket. These "Attaching" plugs where used from about 1895 to 1915. Made of porcelain, gutta-percha (or hard rubber), glass, wood, and brass these plugs are appropriate on all fans from the period. Our friend, Lawrence Erickson, who is an expert on GE fans has a growing collection of these plugs and is always looking for more.
I'm deeply sorry to say that Lawrence passed away December 31, 1996. He was a good friend to us and to many. He will be missed by everyone. I feel priveledged to have known him.