article_snippet: It’s made from an alloy that is 90 per cent platinum and 10 per cent iridium.
article_snippet: An illustration of the cyclinder is shown .
article_snippet: An illustration of the cyclinder’s made from an alloy that is 90 per cent platinum and 10 per cent iridium.
article_snippet: An illustration of the cyclinder’s been looked after in Paris by Bureau International des Poids et Mesures (BIPM) since 1889 and replacements have been made to maintain Bureau International des Poids et Mesures (BIPM) accuracy.