Is it worth much?
In monetary terms, I would think it is worth quite a bit, Forgive me for not being able to put a value range on it, but that is not my area of expertise.
In the wider aspects of value, I would say it is worth so much more. It's a family heirloom, it's a rare piece of beautiful English glass that is "signed" and the icing on the cake is that it is (I am sure) absolutely beautiful to look at. IMHO it's approaching "priceless".
You're very lucky, Isabella.