In addition to a list of requirements or specifications, it is always wise to have some master samples of the product you want to inspect available the day of inspection.

These precious master samples (called also golden or reference samples in the business) will help you compare what has been agreed between you and your supplier with the current production and also to avoid any misunderstandings
from: Asiaqualityfocus

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Note added at 2 Stunden (2019-07-13 13:30:15 GMT)
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A golden sample is a sample produced by a manufacturer that is perfect in almost all ways, so that when evaluated (by clients, competitors, inspectors, media, etc.) it can be tested and receive a high standard review. The term golden sample can also be used to describe a product that is a very rare find and is perfect in almost all ways and has been found just by chance. Contract Manufacturers and Original Design Manufacturers use the term golden sample to describe the final sample that is sent to the customer or OEM for approval before mass production.
from: NLP notes

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Note added at 2 Stunden (2019-07-13 13:32:12 GMT)
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https://www.intouch-quality.com/blog/how-importers-minimize-...

Approved samples are so effective at reducing product defects because they serve as a standard by which mass-produced units are later evaluated. Factory design and engineering staff typically create product samples before mass production of an order starts. These samples typically closely represent the supplier’s understanding of what the buyer wants. The supplier then sends the samples to the buyer to verify a number of qualities, such as:minimize product defects with golden sample

Parts and materials used
Adherence to product specifications
Proper functionality, and
Any complementary designs, branding and artwork for their product

Once the buyer is satisfied with a particular sample, that sample becomes the approved sample, or “golden” sample. The buyer sends this sample back to their supplier and authorizes mass production.