The correct answer isD. The edition specified in the engineering design. In API source inspection practice, the inspector does not choose whichever code edition appears newest or most convenient. The applicable requirements are the ones defined by thepurchase order, engineering design documents, project specifications, approved drawings, and referenced codes and standards identified for that job. Source inspection is a verification function, so the inspector must confirm compliance against thecontractual and technical basis of designestablished for the equipment being manufactured.

This is important because different editions of the same standard may contain different rating rules, test requirements, construction details, or acceptance criteria. If an inspector were to apply the latest edition without project authorization, that could create conflict with the approved design basis and lead to incorrect acceptance or rejection. Likewise, the edition found at the point of use or supplied by the inspection agency is not automatically controlling unless it matches the project's specified design basis.

Therefore, for inspection and quality surveillance of electrical equipment, the governing edition is theedition specified in the engineering designand related contract documents.