Mechanical odometer/cluster failure and mileage authenticity

Early cars used plastic-geared mechanical odometer clusters that frequently broke, often under warranty and reportedly if the trip odometer was reset while moving; Mercedes replaced many with digital clusters via a documented VIN-based warranty program that carried the stated mileage forward. The upshot for buyers is that a swapped cluster can make true mileage unverifiable, so Carfax cross-checks and cluster documentation are recurring due-diligence themes.