Question: when did nickels stop being made of nickel
[{'answer': '1942', 'provenance': [{'wikipedia_id': '358546', 'title': 'Nickel (United States coin)', 'start_paragraph_id': 45, 'start_character': 159, 'end_paragraph_id': 45, 'end_character': 163, 'bleu_score': 1.0, 'section': 'Section::::Jefferson nickel (1938–present).\n'}]}, {'provenance': [{'wikipedia_id': '358546', 'title': 'Nickel (United States coin)', 'start_paragraph_id': 45, 'start_character': 0, 'end_paragraph_id': 45, 'end_character': 967, 'bleu_score': 0.988668097924812, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 1034981083312537498}, 'section': 'Section::::Jefferson nickel (1938–present).\n'}]}]