Question: when was the last 50 cent piece 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': 6, 'start_character': 0, 'end_paragraph_id': 6, 'end_character': 946, 'bleu_score': 0.9476559422809081, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 7676018116934074755}, 'section': 'Section::::Circulation.\n'}]}]