Physikalisch-Technische Bundesanstalt

Our dummy is very hard to carry away – and it thus is already much safer than the international kilogram prototype in Paris which could easily disappear would it be displayed. And this would be a catastrophe, since it is the sole international standard for the mass. It is true that it is stored under three glass jars in a safe two storeys below the earth's surface and that it is most carefully looked after, but every body is subject to changes. The redefinition of the kilogram on the basis of fundamental constants is being feverishly investigated. Until these investigations will be successful, the PTB maintains the national standard, after all, under two glass jars and has it linked up every ten years with the prototype. Of the same weight are the standard measures with which all weighing instruments used in commercial and official transactions are checked. So you can be sure that even the special offer of two pounds of coffee one day will counter-balance the prototype kilogram in Paris within certain tolerances.