looking at my link (which you can probably re-arrange yourself in order to access) - there doesn't appear to be a backstamp forming a circle containing words, as such. VSL did/do produce a paper label which contained their name in full plus the word Belgium - all arranged in a circle. What is this pattern that "seems to be right for VSL?"
Almost all of their backstamps were/are stylus formed, but an acid one was produced.
Regret that I'm the least knowedgable about Belgian glass - so unable to comment with any authority - I think this is the blind (me) leading the not quite so blind
However, it's a very nice vase - was it that town we both know of, again.