I was under the impression that it is THE CAR that is insured
OC in Poland is what they call "liability" or "third party" in other countries. It is the minimum requirement for a car to be driven legally, and covers only damages caused by the subject car to others
if the driver of the subject car is at fault, hence the name liability or third party.
It does not
cover damages to the car subject car (those can be covered by AC, comprehensive or extended coverage).
Usually they calculate the cost of OC based on: driver's age, number of years in possession of a driving license, number of years without claims, location, engine size etc. It is NOT based on the value of the subject car. You can buy a car for 5.000 zl or 100.000 zl and pay the nearly the same amount for OC.
When they calculate AC the value and specifications of the subject car are taken into consideration.