The "tumble-ups" I've had in the past were designed to function without a separate stopper. That being said, I would be leery of this one as being a true antique. As a pretty piece of decorative glass, it might be worth what they are asking.
(I found it curious when checking completed sales of this type of item, I see an identical set was sold by another seller. In comparing the auction photograph from the two sellers...they are the same, even the shadows cast. Hmmm?)