Interesting tumbler - but, sad to say, it's not listed in the book, so can't at the moment provide name of Registrant or exact date it was Registered with the BoT. For whatever reason this situation occurs occasionally, and means that you will need to visit The National Archives in west London, enroll to acquire a reader's ticket, which enables you to research their archives. When you have found this particular entry - take photos of the original factory drawings, then return here to post high resolution pix and provide us with an essay with details of provenance and its Belgium history etc.

Joking of course - can say that it was Registered some time around third week of May 1893, but that's the limit for the moment - this will need to wait until I'm at Kew some time in the coming weeks.
Not that I'm suggesting your acid etching is wrong, but know that some drinking glasses etc. from around this time - Sowerby for example - did use sandblasting as a means of decorating their glass (through a stencil no doubt). Sand gives a much coarser appearance on the glass - acid is smoother. Am sure you're correct with acid etched on this occasion.
What a come down for VSL - to be seen knocking out such cheap tourist pieces - what will Anne Tique think.

Edit - try to diffuse the light, which is masking much of the etched scene - it creates glare that reflects back to the camera. It would be good to see the decoration in full.