David Loebl Schindler & Sons 1913 London vase amethyst/cranberry

This is an interesting one for me: amethyst ground and cranberry submerged colour. I don't think that the sun in the UK is ever enough to do this sort of thing, otherwise we would see a lot more amethyst Edwardian glass, at least I think.
It isn't neodymium, which was my first thought, but it is clearly hallmarked for London 1913 "s". The silversmiths mark is indistinct but is - with the eye of faith - and I have seen pairs similarly marked, one clearly, one indistinctly, David Loebl.
A clearer impression of his mark on the same shape in clear but dating 1920 is shown in pic 4.
Maker?
Very modern in design outlook.
It is 21cm tall.