The Altimeter in the Apollo CM (panel 1) was operational below 50,000 feet. Therefore it was only used by the crew during the early stages of initial powered ascent and then again at the very end of the mission. For the rest of the mission the altimeter was typically covered by an aluminum stopper.
This stopper was flown to the moon on the Apollo 12 mission. It was acquired from the personal collection of Apollo 12 Command Module Pilot Dick Gordon.
The accelerometer (G-force meter) was also only used in the early and late parts of the mission and had a similar, but slightly smaller, stopper.