Ming was located in 2006 as part of an expedition to Iceland. Researchers, unaware of its age or significance, accidentally killed the animal when opening it to investigate its age by literally counting its rings. At the time, scientists pegged Ming's age at 405, but the most recent studies indicate that Ming was, in fact, 507 years old.
The discrepancy came from differences in the types of counting. Scientists have established that ocean quahogs can be dated by counting the number of rings in its shell. It's long been presumed that the most accurate dating comes from counting the rings in the interior of the shell, an area protected by ligaments. But because Ming was so old, the rings were compacted into a few millimeters. Scientists decided to undertake a more accurate count by totaling up the rings on the outside of the shell, and carbon-14 testing confirmed that count. Scientists can also see climate changes evidenced in the rings and can use the oxygen isotopes embedded in the rings to determine the ocean temperatures during various times in Ming's life.
The ocean quahog exhibits what's referred to as negligible senescence, which is roughly defined as not exhibiting any measurable decline in survival characteristics such as strength, mobility or reproductive capabilities. Ocean quahogs live roughly five times longer than humans.