Internal design and commissioning procedures, the project history showing which plants he brought online, training material he wrote, internal fault and deviation records, and a technical director's letter linking each item to the American work.
Documents that could only exist inside this company
Hypothetical example: the engineering department keeps commissioning checklists, as-built control narratives and a fault database built from its own installations. Those are exactly the right exhibits, because they cannot be found anywhere else. Export the versions he authored, the project files that name him, the internal course material and any records of training delivered.
Add a letter from the technical director connecting each document to a specific task at the American plants, so nobody has to infer the relevance. Include the corporate ownership documents and the payroll for the qualifying year, since those are tested at the same time. Manufacturer manuals, published standards and industry training certificates describe knowledge available to everyone and should be kept out of the specialized-knowledge section.