A unit that leaves the country for repair and comes back is only defensible if the record can prove the same physical article returned and only the described work happened. Model that proof as assertions bound to a serial number, not as a note on an order.

The invariant lives on the serial, not the order

An order is a container for commercial intent. A serial is a container for identity. When a unit crosses a border twice, the question a reviewer will eventually ask is not which order it belonged to but whether the thing that came back is the thing that left. Attach the claim to the serial and the order becomes a pointer to it.

The claim itself has two halves. The first half asserts physical continuity: this serial left, this serial returned, same article. The second half asserts work scope: the operations recorded against the serial are the only operations performed.…