Apollo APS Checkout Panel

With two Modules of Fuel and Oxidizer valve controls. Wondering why it has Stage 1,3,7, and 8? I am starting my research on this artifact.

Update from Jonathan Ward (thank you!): “The APS is the Auxiliary Propulsion System, which is on the S-IVB. There were two APS hypergolic engine modules on the aft skirt of the S-IVB. Each module had three attitude control engines and one ullage engine. That’s why there are 8 “stages” on the panel – 2 APS x 4 engines each. The APS controlled the S-IVB in yaw, pitch, and roll during the transposition and docking maneuver. They also were used for ullage before firing the S-IVB’s main engine.”

It is stamped with Serial No. 3, dated October 26, 1964.