Opal Ring | PP?

by Jacqui cottingham
(East Sussex uk)

I have a black opal ring 9 carat gold ring 4.4grams hallmark is 9 then .375 then anchor then z and as in above separately it has PP = or it could be PF = and on the other side it has 768 I would love to know about it but have really struggled to find any information, would anyone be able to help ? Thanking you in advance