As defined by NIST, "Traceability requires the establishment of an unbroken chain of comparisons to stated references." Essentially, traceability is documentation showing a link to a known standard. This master standard can then be used to certify another vessel's accuracy relative to that known standard.
In the USA, national standards for weights and measures are maintained by the National Institute of Standards and Technology. Most countries have their own institutes for maintaining standards, all which can be linked to international BIPM laboratories in France. The Bureau International des Poids et Mesures (BIPM) was set up by the Convention of the Metre and has its headquarters near Paris. It is financed jointly by the Member States of the Convention and operates under the exclusive supervision of the CIPM. Its mandate is to provide the basis for a single, coherent system of measurements throughout the world, traceable to the International System of Units (SI)