The actual grading system depends on the type of item being graded. Authentication is a way of determining whether an item is genuine and described appropriately. Authentication is very difficult because it relies on the expertise of the authenticators. Because of their training and experience, experts can often easily detect counterfeits based on subtle details. However, two expert authenticators may have a different opinion about the authenticity of the same item.
Verification is a way of confirming the identity and evaluating the condition of an item.
Third parties will evaluate and identify an item through a variety of means. For example, some collectors have their item 'DNA tagged' for identification purposes. This provides a way of tracking an item if it changes ownership in the future. Appraisal services are ways of estimating the value of an item. Appraisers use a variety of methods to appraise items, including expert assessment of the authenticity and condition, and reviewing what comparable items have sold for in the market place in recent months.