How to define PVD Rod scratch test failed or Pass

1.Process:Cell phone shell of SUS 304---Polish----Electronic-polish-----Sandblast -----Silver PVD(2-5um)---AFP.
2.Test requirement: Customer's PVD test reliability test requirement, PVD coating shall endure 4N Rod scratch test , No breakthrough allow.
3.Problem:Due to both of the substance and PVD are silver,so after Rod scratch test ,How to determined Which layer is actually breakthrough, PVD or AFP?