Hallmarks On White Gold Ring

by Rebekah
(Wales, Bridgend )

What is the item?

White gold ring, with stones in

Can you please provide all background information?
received from a friend years ago

What are the markings?

On left side what looks like DIA OR OIA and on the right side
There's- GA- scales which are very worn out, then there's 375 then what appears to be like the sheffield stamp
Thanks for any help.