This is a Belgian mantel ornament, one of a pair - I guess the other was broken: they sometimes turn up as a paperweight that shows signs of having been a mantel ornament. I have one that had a broken stem on top, presumably bearing a crucifix or a sulphide. They are most probably from the Chênée factory in Liege. The factory was set up by Alexander Amiable in 1870 and was called Cristalleries et Verreries de l’Ourthe. The canes are often extremely detailed and high quality. These pieces are rare, but I think at least 30 are known, and most have turned up in Belgium or Northern France (or in the US having been bought from auctions in Europe). A few have turned up in Britain - it could be that they were imported and sold here, but may have been brough back from European tours.
I believe that the 'Islington' attribution came about because George Kulles said he had matched a cane - but he later withdrew the attribution. Bob Hall based his ID of 'Islington' in his book on that evidence and on the European style moulding and cutting of the foot, as far as I know because some Birmingham makers copied the European style (a bizarre piece of logic in my view). I prefer the simple explanation - it looks European because it is European. Of course, calling them Islington did nothing to harm their price: I think a matched pair made $10,000 in one sale when called Islington!
Regarding IGW and Islington, I suspect that Rice Harris did make these IGW weights at the Islington Glassworks in Birmingham, but if you check the known IGW weights they use a very limited set of high quality complicated canes. That suggests to me that Rice Harris may have bought a sample of canes (possibly from a Bohemian factory), made up a horse cane and an IGW cane (which are of poorer quality than the other canes), and used these to make a number of sample weights for sales exhibitions. No orders were ever placed by customers (maybe they were too expensive?), and so no more weights were made. Hence the rarity. Just a theory, but it does explain some of the facts.