To add to that, Alan, I have seen one recently with a splodgy orange centre with three ice-pick features with a bubble - the sort one automatically assumes Indian or perhaps slightly older Chinese, this sort of style, with a Made in Gibraltar label. It really surprised me. No aventurine or other colours.
I didn't buy it, even as an example to photograph, because it had a massive crack right through it, it was far too expensive and my OH would have had kittens if I'd brought it home.
This weight is just far, far too like these generic weights, I would be very surprised if Mr Stuart Clarke had anything to do with it.