Vins are a useful if not insurmountable device in the fight against car theft. The chassis number is etched into some suitably expensive part/parts of the car which lessen its value to the rogue car ringers, by making the job of changing its identity more difficult.
The simple type involves etching all the windows meaning replacement of all the glass, which should but probably doesn't raise suspicions at the retailers.
A more complex type involve a plate from the bulk head which comes through the dash top and is visible behind the screen, again it is very difficult to disguise/replace.
Vins are a recent innovation only becoming common place after the mid 90's.