The Standing Committee (SC) of the Convention has accepted the application of "LGAI Technological Center S.A. (APPLUS)" of Spain to become a Technical Programme Participant (TPP). The status of TPP is granted to Assay Offices of Non-Members of the Convention, which want to regularly participate in SC meetings as well as in the Convention's Round Robin (interlaboratory proficiency testing scheme on precious metals). Alternatively, Assay Offices and Ministries of Non-Members of the Convention, as well as any organisation in the field of precious metal control, can submit a request to become an Observer. Non-Members can, however, not apply the Convention Common Control Mark (CCM) on precious metal articles.
The current TPPs and Observers are:
- Institute of Metrology of Bosnia and Herzegovina
- National Jewellery Quality Supervision and Inspection Center of China (with branch in Shenzhen)
- Assay Office of North Macedonia
- Assay Office of Mauritius
- Assay Office of Moldova
- Assay Office of Mongolia (based in Ulaanbaatar with branches in Bayankhongor and Darkhan-uul)
- Bureau of Metrology, Montenegro
- Singapore Test Services Pte Ltd, Assay Office of Singapore
- ECOMEP Laboratorio de Contraste de Córdoba of Spain
- LGAI Technological Center S.A. (APPLUS) of Spain
- KRISOS (Asociación Española de Laboratorios Acreditados en el Área de Metales Preciosos), which comprises six laboratories in Spain in the field of precious metal control: Instituto Tecnológico Metalmecánico, Mueble, Madera, Embalaje y Afines (AIDIMME), Centro de Laboratorios de Madrid (CLYSIM), Dpto. Verificación y Análisis (SAVECO), Instituto Tecnológico de la Bisutería (ITEB), Collegi Oficial de Joiers, d’Orfebres, de Rellotgers i de Gemmòlegs de Catalunya (JORGC).
- The Gem and Jewelry Institute of Thailand (GIT)