EN 10204 specifies the types of inspection documents for metallic materials. 3.1: Issued by an inspection representative authorized by the manufacturer's quality department, declaring that the products conform to the order requirements, and accompanied by inspection results such as cast analysis and mechanical properties; the document is produced within the manufacturer's system. 3.2: Issued by an independent inspection body or authorized representative outside the manufacturer and with no interest in the manufacturer, typically requiring third-party witnessing of sampling and testing, with the document signed by the third party. Practical differences: 3.1 is low-cost and fast to deliver, suitable for general industrial use; 3.2 offers stronger credibility and traceability and is often used for pressure vessels, offshore engineering, nuclear power, and projects specified by the owner. When purchasing, the contract should clearly specify the required type, inspection items, witnessing method, and document language, to avoid acceptance problems after delivery due to a mismatch in document grade.