[fortyonerag]

Way back when I was green and simple, I worked as an auto elec in a shop servicing a bunch of (dodgy) used car lots.

Resetting odometers was common request, but only the boss would do it

The way the boss used to do it: Get a broken hacksaw blade and grind it down to a thin strip. Maybe 40mm long by say 5mm high. File it down so it's very thin and can be slid between the odometer wheels (without damaging them) to reach the drive gear behind.

By sliding the 'tool' between the odometer wheels it should be possible engage the odometer wheel drive gear and 'flick' it to the desired setting.

Each odometer wheel has its own gear so each odometer wheel must be manipulated to get the desired setting.

It's very possible this technique damages the odometer.