Question: when did us stop using silver in coins
[{'answer': 'late 1965', 'provenance': [{'wikipedia_id': '10566622', 'title': 'Coinage Act of 1965', 'start_paragraph_id': 3, 'start_character': 44, 'end_paragraph_id': 3, 'end_character': 53, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '10566622', 'title': 'Coinage Act of 1965', 'start_paragraph_id': 3, 'start_character': 0, 'end_paragraph_id': 3, 'end_character': 346, 'bleu_score': 0.9669306597086381, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 13691381681185050533}, 'section': 'Section::::Abstract.'}]}]