I have seen this signature several times - usually as "Cristal Guerandi" - in one case attributed to an Anna Guerandi in Bristol. I cannot find anything about her on the web, though.
One weight also had a sticker "Ortloff" on the base (a shop ?).
What confuses me is one paperweight signed "Farfalla Guerandi". Now - Farfalla is well known paperweight dealer in Germany, and many paperweights they sell have their butterfly logo plus their name etched on the base ... but I have never seen farfalla from the artist's hand added to his/her signature (apart from this one).