this one says it is Mont Joye (no comment in the sale blurb on whether it is marked though !) but it is the shape I was thinking of?
https://www.cottoneauctions.com/lots/36943/mont-joye-vase-with-painted-enameled-chrysanthemums
this advert shows the shape,or similar in the Legras book possibly?
https://www.tweedehands.nl/antiek-kunst/antiek/glaswerk-kristal/antieke-art-nouveau-montjoye-legras-320403407.html
Both vases are made by Legras and are the same model, vase 'Olga'.
Just for the occasion …. It's a bit confusing but Legras was absorbed by Souchon-Neuvesel and they were part of the 'Verreries de Saint-Denis et de Pantin réunis'.
Auguste Heilgenstein collaborated between 1926 and 1931 with S-N and created a series of thick glass items, often coloured with enamel powders and acid cut. A small production, rarely signed by his own name (Heiligenstein) that was given the name 'Montjoye et SD', signed often by diamond point or gold paint.
Montjoye often does use long petaled chrysanthemums in their decor, much more than Legras, but in both cases the enamel is much thicker. The enamel of the vase in question is much thinner. Landscapes at either production are very often acid cut or transfer printed before applying enamel powders (Delft series).
Of course the decor of the vase in question is completely different, but i'm only trying to point out the difference of the enamel and in any case, this shape is not unique to either Legras or Montjoye. The gilding on the rim at Legras and Montjoye is always powdered (putoisé) which clearly here, is not the case.
Having said all of that, I couldn't tell who has made this vase. I only have a few examples of Heckert in Das Böhmische Glas, and the decor on the vase in question looks a bit less 'neat'.