PD on a ring ordinarily signifies palladium. Your ring could be palladium-plated if it has PD penned about it. HK is often a trademark that means Harriet Kelsall. They design and supply jewellery everywhere in the UK and also to other sites also.  Can “JP” also stand for another country? https://angeloqdqal.uzblog.net/the-ultimate-guide-to-jp88-50650991