Most likely by Welz.
Described as 'late 1800s' by the seller, I'm not sure its that old, I would guess anywhere from then up to the '20s,
This vase, although art nouveau in style, has a newer 'feel' to it than the Deco style vase next to it, shouldn't that be the other way around? :-S
I'm not a glass expert, just a glass lover, particularly interested in Victorian glass:)