Yes, I agree that shape HE is what it most resembles. But its size (large) is not in the Monart catalogue. If it was made in the Monart years, then it is a new entry for "size variation". If it was made in the Ysart Brothers (Vasart) years then it was "along the lines of the HE bottle".
So, who bought such an ugly thing with cracks all over it? Oh yeah, it was me ...

And it arrived with even more damage! Sadly it was posted with the stopper (which is heavy) taped into the neck and when opened, the whole neck was separate from the body. There are also two additional major cracks in the side of the body that was not shown in any of the listing photos.
I have settled the matter of the additional damage with the seller so this is not a problem that needs comment here.For me it is still an interesting piece academically because it is the first Ysart bottle (which is not an inkwell) that I have seen decorated solely with millefiori canes.
The striped appearance to the neck is formed by stretching the upper row of canes from the shoulder and applying a slight twist. The effect is like an "experimental" form of the striping in the regular Vasart (1946 - 1956) inkwells. The interior has a layer of off-white (grey) which, due to the blowing, is more solid at the neck, then more sparse at the body and more solid again at the base. But it does not seem to be the fairly solid appearance of the off-white used in some early Monart pieces, but I have only seen a very few of those, so cannot comment much on that aspect.
However, the same type of (powdery) grey is known in some paperweights which I believe were made by Salvador Ysart. That may, or may not, be a help in shifting the dating of some of the paperweights. Much more research is required.
I will soon be purchasing some decent glue and spending some time doing "museum style restoration" - just for the fun of it and to try to preserve an interesting piece that might at some stage assist with the ongoing research into "Ysart oddities".
And for the record, under uv light, the clear glass fluoresces like other Ysart items from Moncrieff's and Ysart Brothers (Vasart), so it is certainly not Vasart Ltd or later.