Hi Rose, I have attached a better photo of the underside of the base. I had ruled out Carnival glass as this is not iridescent but a very clear blue. John
Hi thanks...

Are these on the underside of the glass, OR on the top side of the bottom rim. You can clearly rub your finger along the very underneath of the bottom and feel these???
I take it you are over-the-pond from Me here, as for what glass company might have made this....
Take a peek
HERE, AND SCROLL DOWN to see IF you can see any similar Glass patterns, as I am not sure what the pattern of yours is called ??
Looks like a few patterns there......might help
