Here’s an underwater-archaeology version of the classic before-and-after picture pairing, courtesy of 137 years’ worth of concretion on the one side and painstaking, meticulous conservation efforts on the other. One of a number of interesting finds to emerge from the remains of the Confederate submarine H. L. Hunley, this brass oil can first appeared to conservators at Clemson University’s Warren Lasch Conservation Center as a mysterious and inexplicable blob protruding from the sub’s dashboard. X-rays subsequently revealed the artifact pearl inside the concretion oyster. As an added bonus, the can was still half-filled with oil from the 1860s. Thanks to the durable qualities of brass, the oil can handled its restoration quite nicely, and with relative ease compared to sundry other objects—from pocketknives to a bandanna—found amid the Hunley wreckage. Yet its very presence there is a mystery in itself.