Upon changing bulbs in the big hallway chandelier the sockets got my curiosity. The chandelier is probably as old as the house, making it 92-93 years. The sockets are the old kind, brass with a porcelaine collar screwed to the outside of the thread that should in theory cover the bul thread and act as a spacer between socket thread and outer shell. There are two sizes of collars, and this one exposes a real lot of thread! So I started suspecting it could actually have been intended for ES26 bulbs! I don't have any to prove i though.