The materials used don't have to be secret, often it's the way to manufacture that's kept secret.
It's similar with banknotes. The materials used is public knowledge (and parts of it patented), but manufacturing is a secret to avoid counterfeiting.
It's similar with banknotes. The materials used is public knowledge (and parts of it patented), but manufacturing is a secret to avoid counterfeiting.
If you don't have a list of all the input raw materials, intermediates, by-products, impurities, surface materials that can leech into the final product, etc; you can't test for them.