The S-IVB was the third stage on the Saturn V and second stage on the Saturn IB launch vehicles. Built by the Douglas Aircraft Company, it had one J-2 rocket engine. For lunar missions it was fired twice: first for Earth orbit insertion, and then for translunar injection (TLI).
Heroicrelics posted a good summary of the helium system that kept the liquid oxygen (LOX) tank pressurized: “While the S-IVB’s J-2 engine fired, the LOX tank pressure was maintained by cold helium spheres located in the liquid hydrogen (LH2) tank: Helium from the spheres was expanded by the J-2’s heat exchanger, after which it was routed to the LOX tank. The LH2 tank was pressurized by drawing gaseous hydrogen directly from the engine.”
On this control panel, there is a “KSC Operational Check” sticker on each pressure gauge. They appear to say that the next check is “ASTP” the famous Apollo Soyuz Test Project that ended the space race. I am still researching this artifact and would appreciate any perspectives others might have.
An artifact from the Future Ventures’ 🚀 Space Collection, soon to been on loan to SETI for their new HQ.
Bottom left sticker shows 1972 modifications: 
and again 12/4/72 (three days before Apollo 17):
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