It's a "Two-tone, blue and amethyst, strapped, attenuated bottle", John. :thup:

It's fabulous.

These are quite scarce and very highly desirable pieces. They mostly seem to be dated '74 and '75, (I don't
think I've seen one which is later - but I'm open to any new info). This is the period when Eric Dobson was in charge, before Joseph Said took over, and Eric Dobson a fair amount of design input, despite that not being his official role (he designed the Tiger pattern).
You'll have to check it over very carefully for damage to the strapping, but even if there is a little, it shouldn't matter too much for sale purposes, given their scarcity - and fabulosity.
They often have a maker's signature on the base as well as the date. Either Dobson's or Said's mark.
It there any silvery iridesence on the outside?