Question: when were the last silver half dollars made
[{'answer': '2002', 'provenance': [{'wikipedia_id': '374699', 'title': 'Half dollar (United States coin)', 'start_paragraph_id': 2, 'start_character': 246, 'end_paragraph_id': 2, 'end_character': 250, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '374699', 'title': 'Half dollar (United States coin)', 'start_paragraph_id': 2, 'start_character': 0, 'end_paragraph_id': 2, 'end_character': 631, 'bleu_score': 0.9131241013715451, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 12659919761218178028}, 'section': 'Section::::Abstract.'}]}]