Makers marks on 1960s modernist silver ring

Got this gold on silver 1980s modernist ring which im researching but woth no success. It has london import marks and the letter h dates 1982. I believe the maker mark is AD?

Anybody has the reference books?
Any info input is welcome

 

They are import irish hallmarks I can see on the last picture.
It's a hallmark AD in a square with cut orners I can't find from where it comes.
It's more difficult with modern silver or gold jewellery to find the original provenance than with 100 years old and more.

 

London import mark, not Irish.

 

Right, it's the Britannia standard, and I don't know why it's under Irland in my memory booklet…