Compliance of Assay Offices

The Convention being a technical agreement, the onus to implement the Convention’s requirements is with the Assay Offices, which are the designated control bodies in each Contracting State in charge of applying these requirements.

Article 5 of the Convention defines the conditions that an Assay Office, which has been authorised to apply the Common Control Mark (CCM), must meet. These conditions are:

Essentially, this means that authorised Assay Offices must be technically competent and independent not only at the time of their appointment (i.e. when the Ministry grants them the authorisation to apply the CCM) but at all times thereafter.

Technical competence (Round Robin)

The technical competence of an Assay Office is essentially demonstrated by the results obtained during its participation in a proficiency testing scheme. According to ISO/IEC 17043:2010, a proficiency scheme is an “evaluation of a participant performance against pre-established criteria by means of interlaboratory comparisons”.

In the Convention, the proficiency scheme is called a “Round Robin”: it is an exercise in which a laboratory is subject to a blind evaluation aiming at verifying the level of knowledge and expertise in a particular field.  The laboratory will get various samples on platinum, gold, palladium and silver and will have to determined their fineness by means of two analyses: destructive and non-destructive (e.g. XRF). The laboratory will report its results, which will be given a score (“Z-score”): if it is equal or higher than 3, it will be considered as a poor performance and the laboratory will be asked to carry out an investigation and take correction action.

A lack of technical competence can also be sanctioned under Article 9(1) of the Convention, which provides for a consultation / dispute settlement system regarding the implementation of the Convention’s technical requirements, in particular the application of the Common Control Mark (CCM). If a State or Assay Office has reasons to believe that another Assay Office has not applied the CCM in line with the Convention’s requirements, it can ask for clarifications. If these clarifications are not satisfying, the matter can be referred to the Standing Committee, which can make recommendations.  If these recommendations are not implemented, “additional surveillance of articles of precious metals marked by that particular assay office” can be introduced. If there is “evidence of repeated and grave misapplication”, then the CCM articles of that particular assay office may be refused.



The Convention has been a pioneer at the international level in establishing the principle of independent, third-party control in the field of precious metal control.  The principle as such is at the heart of Assay Offices, which exist in many European countries since the Middle Age. The principle is still valid today.

Article 5 stipulates that the management and staff of an Assay Office must be independent from Trade. This is an essential requirement to guarantee that the Assay Office is indeed an independent “third party”. The status is verified by the competent Ministry (or Supervisory Authority), notably based on the Standing Committee’s guidelines (see below) as well as a questionnaire, which the Standing Committee has developed and which must be completed at least once every 5 years. The replies to the questionnaire are circulated to all Members of the Standing Committee.

The Guidelines for the Assessment Requirements of Authorised, Independent Assay Offices have been primarily drafted in order to assist the Inspection Team, when visiting an Applicant State, to assess if the local Assay Office is “independent” in line with the Convention’s requirements.  However, the Guidelines are also applicable to already appointed Assay Offices, which have been authorised to apply the CCM in line with Article 5 of the Convention.

The Guidelines are based on the Convention’s requirements, in particular Article 5, as well as international standards such as ISO 17025 and ISO 17020. They define the requirements of independence for Assay Offices, which must comply with “Type A of inspection body”, as defined in ISO 17020 “General Criteria for the operation of various types of bodies performing inspection”. 

The Guidelines examine the many aspects related to the independence of Assay Offices starting with management and staff, good governance, quality management, etc.  For the Guidelines, visit the page dedicated to the "Compilation of Acts" of the Standing Committee.