The design of your weight is not a "Fountain". It is a "Double Harlequin" and of a form that was first made by Paul Ysart in the 1930s. But I think this one may have been made by Salvador Ysart, not Paul!
As I was replying Frank made a good observation about the canes. The canes that are clearly visible in your photos do indeed match with what are usually said to be Vasart canes (from the Ysart Brothers Glass period 1946 - 1956). However, many "early Vasart" canes can be found in certain types of pre-war Monart bottle stoppers, so the canes in your weight could easily have been made in the pre-war Ysart years.
It is the overall look of the weight that suggests Salvador's work to me. However, from a top view, looking straight down, and from a bottom view looking square on to the base, many people would say this is by Paul Ysart! Also, the fact that the upper layer is set on a white ground is something that ties in with several examples of this design made by Paul. But whether the white layer is actually formed the same way as those I have seen in Paul's work cannot be confirmed from the above photos.
If possible I would like to see photos of:
- All the canes - a series of shots around the lower section and four closeup shots looking down on sections of the upper layer
- A straight-on side view, similar to a view you have already given but with the top and base of the weight fully in view
- A closeup shot of the underside of the white layer