Ohio Precious Metals Silver bullion. Ohio Precious Metals is committed to providing high-quality gold and silver products. Based in Jackson, Ohio, OPM has been in the precious metals industry since 1974. All their products meet the ASTM B562-95 and ASTM B413-97a standards for purity. Additionally, OPM is a certified Responsible Source Refinery and offer Conflict-Free and Responsibly-Sourced products. OPM has achieved good delivery status with Comex.