I've just looked through the small and larger books, but wasn't aware of definitely seeing anything with this flower head design of wheel engraving,
but that's not to say it isn't from the Powell's, and John is better informed as to their output so might have the answer. The Company did produce a lot of art nouveau/arts and crafts style designs during the 1890s, often on thin clear glass, and it would be very interesting to know the source of the provenance/attribution the online seller has for connecting their glass with Powell's.
This one does have the Webb/arts and crafts/Powell appearance of thinness etc., but we need a source of genuine provenance to feel safe in attributing to you know who.
You might try the V. & A. on line archive - believe it's possible to access their collections on the screen.
Sorry this is unhelpful, hope someone else might offer suggestions.
