Yes, I remember reading about the various sphinx discussions.
His sturgeons are 'snub-nose' sturgeons according to this link (source - Linda Hall Library) and they do not exist.
So ... given that the modelling of your lamp is a non-existent 'snub-nose sturgeon' as well, there has to be a link somewhere. Either his patent ran out or was never patented, or the glassmaker thought they'd make a good souvenir?
https://www.lindahall.org/george-vulliamy/Scientist of the Day - George Vulliamy
May 19,2015
Can you find out what the patent is via the metal class patent? That might tell you as the glass company may have deliberately registered it in the wrong class.
Also he designed the camel benches as well. Any makers made camels that you know of?
It might be worth having a good look to see if anyone copied his sphinx exactly as iirc there are differences with all of them. I'm thinking that angle because someone seems to have replicated his Sturgeon design with great abandon. I mean it's not exactly a small piece that wouldn't get noticed is it? Like say a Burtles and Tate swan or something.
I wondered if his might have been similar to the Saint-Louis Sphinx? didn't that come in a matt black? Nope not the same modelling.