I'm surprised it has the reg number on it. I have had three unmarked PV lampshades through my hands, two as lampshades and one (168130) as a vase, mounted on a silverplate stand. All three were the acorn shape, supported by screws from a top ring, unlike yours which is supported by the lampholder.
Prior to your find I had assumed that PV had not used the reg number as it could create a hot spot when lit.
Is it all press-moulded, or is there some cutting on it?
Nice find. Please let me know if you ever decide to part with it.