Topic: Maker of mysterious moody paperweight ?

[paperweights]

Thanks to user9318, Lustrousstone, and Nick77 for your comments.  I'll take them in order. 
I agree the middle mark appears to be the Brittania mark.  I thought that was discontinued in 1719, but maybe this is a modification. 
And to Lustrousstone, I agree that the assay or quality mark doesn't make much sense for silverplate, even Sheffield plate.  Maybe Sileda had their silver assayed as used for other items that were silver and was confused (or meant to confuse) buyers when they put it on this item.  As I said, the purpose of the middle mark was a mystery to me. 
And finally Nick77, thank you for your ID of Geurnsey Island studio glass as the likely maker of the paperweight. 
I can't believe I reopened a four year old thread, but sometimes things kick around for a while.  When I found the paperweight again in my deep storage I decided to put some time into getting resolution.  Thanks everyone.