Called the IPK, the standard (What?) is a platinum-iridium cylinder at the International Bureau of Weights and Measures in Sevres France?
Standard (metrology) An example of a primary standard is the international prototype kilogram (IPK) which is the master kilogram and the primary mass standard for the International System of Units (SI). The IPK is a one kilogram mass of a platinum-iridium alloy maintained by the International Bureau of Weights and Measures (BIPM) in Sèvres, France. Another example is the unit of electrical potential, the volt. Formerly it was defined in terms of standard cell electrochemical batteries, which limited the stability and precision of the definition. Currently the volt is defined in terms of the output of a Josephson junction, which bears a
International Bureau of Weights and Measures that meet normally biannually, which is in turn overseen by the General Conference on Weights and Measures () that meets in Paris usually once every four years, consisting of delegates of the governments of the Member States and observers from the Associates of the CGPM. These organizations are also commonly referred to by their French initialisms. The BIPM was created on 20 May 1875, following the signing of the Metre Convention, a treaty among 59 Member States (). It is based at the Pavillon de Breteuil in Sèvres, France, a site (originally ) granted to the Bureau by the French