Caithness, I believe. Sarah Peterson.
Seems related to this piece on Scotland's Glass.
https://www.scotlandsglass.co.uk/cms/index.php?page=shop.product_details&flypage=flypage.tpl&product_id=3440&category_id=33&option=com_virtuemart&Itemid=6Sarah trained with Bertil Vallein to make sand casts. Which kind of explains their quality a bit, along with her innate talent.
Please, please do not try to fiddle with it or "clean" it up beyond what you can get off with biological washing liquid and a soft toothbrush.

Dartington took over Caithness, but now seem to be based in Crieff in the Caithness Visitor Centre.
It is Sarah herself who makes the sand casts. I don't know why there would be one she hasn't signed, unless there is some sort of miniscule flaw rendering it a second. She is the artist, designer and maker holding everything together, as far as I know.
The kind of folded over double construction of the layers of glass in the body is the same as the sand cast I have. I really don't think it's a crease, it's part of the construction.
As are the few bits of sand left stuck to the bottom.

I did say something about Sarah P in the thread ekimp posted.
To my knowledge, she is the only person who makes the sand casts. They are one-off, artist made pieces, every single one unique because of short runs and individual variation. They are not part of the general runs of "bread and butter" pieces all the makers can produce.
I was lucky enough to meet the Caithness engraver, Bruce Walker in Kirriemuir a few years ago and we had a lovely long chat about Sarah P. He told me a good bit about her, which is what I have repeated here.
His admiration for her and her work was palpable, and I hope he enjoyed me being a rapt audience, eager to hear all he could tell me.

Some casts may have been sold under the Innovate name, but they were not made in China.
