Question: when did they stop making silver dollar coins
[{'answer': 'December 11 , 2011'}, {'provenance': [{'wikipedia_id': '374778', 'title': 'Dollar coin (United States)', 'start_paragraph_id': 2, 'start_character': 0, 'end_paragraph_id': 2, 'end_character': 603, 'bleu_score': 0.9642618757124931, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 6466419743763081512}, 'section': 'Section::::Abstract.'}]}]