This set was made for a 35th Wedding Anniversary. Coral is the symbol for this anniversary and jade is the modern gemstone for it, or emerald traditionally.
The porohita/circle was chosen as a symbol of completeness, one to be worn by each in the marriage.
The pounamu was selected for its patterning, which gives it amazing character and resembles the moana/ocean when viewed from above which is the link to coral. The cloudy flower patterning is caused by layers in the pounamu, they can be fiddly to carve as they have a tendency to flake off if you get the angle wrong.