A 58-year-old man presents with progressive dyspnea and dry cough for 2 years. He worked in a shipyard for 15 years (1985–2000) as an insulation worker, then changed careers. HRCT chest shows basal subpleural reticulation with honeycombing and pleural plaques. PFTs reveal a restrictive pattern with reduced DLCO. The ferruginous body shown in the diagram is consistent with asbestos exposure. Which of the following aspects of **D** (Asbestos Exposure History) is MOST critical for establishing the diagnosis of asbestosis in this patient?