Apollo Command Module Block II Service Propulsion System (SPS) Propellant Quantity and Utilization display gauge used as a ground test unit, marked on the reverse with the control no. "ME181-0139-ADT." The box measures 4.75″ x 6″ x 5.75″, and marked on the side in red paint: "For Ground Only." The gauge has a display for remaining oxidizer and fuel, a test switch, a dial to indicate an unbalanced mixture, and three switches along the bottom to control the oxidizer flow, as well as the mode of the PUG. Located on Panel 3A of the Command Module main control panel, this gauge would measure the remaining fuel and oxidizer quantities and display and control the fuel/oxidizer mixture ratio.
