Thu, Jun 27, 2013 12:00 - Imperial Petroleum, Inc. (IPMN: OTC Pink Limited) - Tier Change - The symbol, IPMN, no longer is classified as OTC Pink No Information. As of Thu, Jun 27, 2013, IPMN resides in the OTC Pink Limited tier. You may find a complete list of tier changes at otcmarkets.com.