When I bought my BMW four years ago (it's an old car, built '98) the history showed two consecutive MOT's where the mileage was listed as 'unrecordable' followed by the next test where the mileage had increased by exactly 10,000m. The tamper dot is showing as well, but for all I know it could be explained by a cluster replacement to rectify the faulty odometer, with the mileage over those two years being estimated.
Anyway the car has been very reliable in my ownership, with zero engine oil consumption, so I'm not concerned if the current 162k is correct.