The Mars Science Laboratory (MSL), aka the Curiosity Rover is something of a robotic geologist, so it makes sense to include the tools of the trade in some form, including a calibration target. For giving a sense of scale with smaller geologic features, pennies are often used for scale, as a common item with a standard dimension. But why is there a 1909 penny on the Rover? That's thanks to Kenneth Edgett, the Mars Hand Lens Imager (MAHLI) principal investigator and an amateur coin collector who appreciates the history of the controversial 1909 V.D.B. Lincoln Cent.
"Howe snapped more than 400 photographs in Moscow and St. Petersburg with his hand held Graflex camera, a state-of-the-art device that allowed its user to shoot without a tripod. His photographs of pedestrians, street vendors and aristocrats are rare glimpses of everyday life before the upheavals of World War I and the Bolshevik Revolution — and sparked huge interest in Russia among history buffs and local museums."