Microdots ?
Didn't Tommorows World (so must be 25 years old) show a system of spraying thousands of microdots with the VIN (look em up kids) all over a car. The idea being you could never remove them all, and only one would be needed to link a gearbox/engine/ECU (think about the last) to a stolen car.
The problem being the second a car is in pieces (where it's worth more than as a car) then the police are on the back foot having to prove where the piece came from.