The pocket paint tester tells you more in a few seconds than after hours of inspection by eye. It tests the thickness of the paint, which is invisible to the eye, and thus identifies formerly damaged, repaired areas. Because even a minor-looking paint touch-up can conceal an extensive bodywork damage repair. A small amount that is well invested, because: You can negotiate the price with proper arguments You have the certainty that you are buying the right car You can refrain from (mis)buying if necessary