Tachometer question

It sounds like the gauge uses a stepper to drive the needle. That is typical for needle gauges in modern cars. They consist of a rotor with magnetic poles, and stator with coils. The coils are driven to step the rotor with a pulse. The electronics initializes the zero position, then steps and micro-steps for desired reading based on RPM. The movement does a fixed value of degrees movement per step, so the movement does not need calibration.