I really don't think IoWSG made mushrooms of this construction.
I'm absolutely sure Mtarfa did, I have one with a red and greenish black interior and this wide clear rim. It's not marked, I don't think, but the colours led me to Mtarfa some time ago.
I can't find it. It's not where I last saw it.
I don't know if Mtarfa used gold and silver foil though.
It could be something from St. John's Wood, who were doing some gold and silver foil stuff under license to IoWSG until it went all pear-shaped.
I know Wedgwood did similar too, but a completely different shape with a big round dome.