Question: when did we get off the silver standard
[{'answer': 'June 24 , 1968', 'provenance': [{'wikipedia_id': '2235798', 'title': 'Silver standard', 'start_paragraph_id': 64, 'start_character': 234, 'end_paragraph_id': 64, 'end_character': 248, 'bleu_score': 1.0, 'section': 'Section::::United States.\n'}]}, {'provenance': [{'wikipedia_id': '2235798', 'title': 'Silver standard', 'start_paragraph_id': 64, 'start_character': 0, 'end_paragraph_id': 64, 'end_character': 247, 'bleu_score': 0.9493253852526031, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 8374852319264164685}, 'section': 'Section::::United States.\n'}]}]