Through detailed conversations within the past five years, the way I have come to understand the initial concern about the condition of the Cartridge is to investigate the Bobbin Assembly.
This is quite different to my old thoughts and methods to be only concerned about the Stylus condition, Mounting! > Wear !
In a Layman description, the Cantilever Anchors to the Bobbin Assembly and sets up the mechanical operation that will enable the Stylus to perform as per the designed for operation.
Any compromised materials discovered at this place in the assembly will be detrimental to the overall performance.
Hence, my skill set does not reach to this level, so I farm the inspection out to a much more reliable assessment, the bonus is the Stylus will also be evaluated along with other materials within the assembly.
When it is viewed with this in mind a Third Party Inspection starts to show its real value to the buyer.