Lamp finial thread standard is weird.

gafftapegreenia

CBMod
CB Mods
Joined
Sep 24, 2005
Location
Michigan
Why the HECK are lamp finial threads 1/4”-27? It’s such an oddball when 1/4”-28 I would consider the “normal” fine thread standard. Is it some other carryover from the gas era? The rest of lamp threading is based on plumbing threads.