Hi Mel, probably impossible to say for sure, but I think it could be Italian/Empoli. The pontil mark sounds and looks about right (ground but not polished), and some tortoiseshell glassware was made by the CLAVE company (quite possibly others too). There was an Italian museum website with a few tortoiseshell examples a while ago, which has since vanished unfortunately.
Not sure about the stopper, but I'd guess at not original, and I'd guess at 1970's-ish.