Question: when did the silver threepenny piece go out of circulation
[{'answer': '1970', 'provenance': [{'wikipedia_id': '221261', 'title': 'Threepence (British coin)', 'start_paragraph_id': 39, 'start_character': 374, 'end_paragraph_id': 39, 'end_character': 378, 'bleu_score': 1.0, 'section': 'Section::::Elizabeth II threepences.\n'}]}]