Can you help me with this O (ouroboros) and AD mark please?

These two applied stamps are on a large trumpet shaped vase in thrown terracotta.  The clay is heavily grogged and a glaze applied to the bottom half inside, which is why I think it is a vase for flowers rather than a garden pot.  One stamp appears to be a logo and the other one appears to have the initials AD.  The vase is beautifully potted and remarkably light for its size.  

I’ve seen this pair of marks before but not IDed it. The O mark is a snake biting it’s tail

Thanks very much. A snake biting its tail is called an ouroboros apparently, an ancient symbol used by Egyptians and Greeks and associated with alchemy amongst other things. Interesting although it doesn't help answer the question!

Helps to have a photo of the base to check clay and construction

Hi
Photo of base here. Thanks.

Cheers Not a wire-cut base. It might not be British