PD on a hoop typically represents palladium. Your ring could possibly be palladium-plated if it's got PD penned more than it. HK is actually a trademark that stands for Harriet Kelsall. They style and design and supply jewellery all around the United kingdom and to other places too.  Can “JP” https://emilioaluck.frewwebs.com/37506853/the-definitive-guide-to-jp88