Just for a bit more info (and confusion):
The Spitfire weights (a few others are known - and I think at least one other is signed "F Eisner") have been one source of specualtion about whether Frank Eisner may have been at Moncrieff's and possible knew, or even worked with, the Ysart men. It is known that Paul Ysart made lampworked Spitfire's in the 1940s, but I don't think there is any evidence that he encased any in weights. If that is true, then there could be many possibilities as to how Frank Eisner obtained the Spitfires, including the idea that he got them from somebody else who may have had contact with Paul Ysart. And, on the little evidence we have, there is also a possibility that some of the weights were not made until long after the production of the lampwork Spitfires.
Lots of guessing, not much factual evidence!