Just to insert a cat among the pigeons, there is a 6-wave jug or tankard amongst all the pieces of glass near the entrance to the old Stuart glass cone tourist attraction - the Red House Glass Centre, I think it's called.
I visited all the Stourbridgy sights (and sites) last year, and spotted it but couldn't get any joy out of the staff. "Sorry, all the records and the Stuart Collection are now owned by Waterford/Wedgwood, and we don't have access to any information."
Another reason to save Broadfield.
There's a long corridor once you get inside the old glassworks proper, at the end of which is a mockup of a Lehr/furnace. Amongst all the pieces of glass sitting among the cinders is the wavy item.
If anyone pops in soon, they could perhaps take a look-see. I assume that everything on display is Stuart, but it could well be a Webb piece included by mistake, of course.