That pwt is most likely leftover stock from St John's glass, from the time after they fell out with MH. There's tons of it appearing on ebay over time.
The green is different, I've got a St John's mouse in green, it's more distempery and slightly opaque. It's not desperately well made and has gold foil on, not silver. Gold is much easier to use than silver.
If it's silver foil on your bit, Trevor, this would most likely indicate a date after the technique for using silver foil was "invented" (or is it re-invented, given it has been used in old Venetian glass?) by MH and William Walker when they produced the Azurene range at IoWSG. I do have some very early Azurene bits, made before thy'd got it quite right, and the foil reacts with the glass to produce coloured effects - yet your piece does not seem to have done this in the same sort of way - it's far more sophisticated.
Pic attached. the one on the left does show clearly what the yellowy bluey colour is that appears - that's the sort of bit that gets broken into the "tectonic plates" and can look like the foil itself.
Something very odd has happened with the one on the right! The silver foil must have vapourised, but it has deposited itself around the top of the piece. They both have both silver and gold foil features - the gold is the stuff that's stayed as foil.