If it's a mechanical one, there's a possibility that it's been repaired or replaced. The mechanism after all these years will likely wear out. At the same time, I know someone with a car whose odometer has been at 249,999km for a few years now.

As for (early) digital odometers, does the soul more specifically exist in the EEPROM chip in the instrument cluster* that stores the odometer data?

*at least on my late-90s car, this is how the odometer/trip meter works.