Bump
I understand tortoiseshell glass is quite rare; which is, perhaps, why I have been able to find out so little about it.
If no maker or other ID, how about a stab at the potential value? - I am about to list it on the big auction house in the sky

Without attribution, and just on its dramatic decorative qualities I am aiming for about £50. Too cheap? Or way over the top?
Opinions very welcome. Thank you.