PD on a hoop typically represents palladium. Your ring could be palladium-plated if it's PD published around it. HK is really a trademark that stands for Harriet Kelsall. They layout and provide jewellery everywhere in the UK and to other spots likewise.  Nation hallmarks: Some countries have their own hallmarking systems. https://hk-futures-best-cryptocur77776.qodsblog.com/37112196/detailed-notes-on-jp88