What do the mark pGDa 18k mean?

The mark "pGDa 18k" typically indicates that the item is made of 18-karat gold, which means it contains 75% gold and 25% other metals. The "pGDa" portion may refer to the manufacturer or a specific design hallmark, but it is less common and could require additional context to identify. It's important to verify these marks with a reputable jeweler or appraiser for precise identification.