A computer-generated image of the International Prototype kilogram (IPK), which is made from an alloy of 90% platinum and 10% iridium (by weight) and machined into a right-circular cylinder (height = diameter) of 39.17 mm. The IPK is kept at the Bureau International des Poids et Mesures (International Bureau of Weights and Measures) in Sèvres on the outskirts of Paris.

The geometry of this computer model was based on the actual specifications being used for experiments in new manufacturing techniques to produce new kilogram mass standards.

Solid model and ray-traced image was created using Cobalt CAD software.

This image was provided by the contributor because of the dearth of uncopyrighted photographs of the actual IPK. This is expected to be a chronic limitation given that…

1. the IPK is stored in a vault nearly all the time,
2. there is no general public access to the BIPM (and certainly none to the vault),
3. and working copies of the IPK are used at the BIPM for routine calibrations for years on-end.