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Certification

Principles

Independence, traceability, mutual recognition: the principles that guarantee the value of an OIMAP certificate.

Updated : October 28, 2026· 4 min read

Why common principles

Letter Box, Ogata Kōrin (1700s)
Letter Box, Ogata Kōrin (1700s)

Trust in a certificate depends less on the paper than on the rules governing its issue. Five principles apply to each file, in every Member State.

These principles derive from Directive No. 2019-07 and the experts' code of ethics. They are monitored by the certification committee and may be invoked by any declarant.

They answer three risks known to the market: complacent expertise, a break in the chain of provenance and the circulation of works of illicit origin.

  • Independence
  • Traceability
  • Reasoned opinion
  • Recognition

The principles in figures

5founding principles
4 yearsterm of an expert's accreditation
5 daysto challenge an expert
30 daysto request a re-examination

The five principles

Lace Towel End (c. 1700s–1800s)1Independence

The expert has no financial or personal link with the work or the declarant.

Adoration of the Shepherds, Bernardo Cavallino (c. 1650)2Traceability

Each step, each analysis and each source is recorded in the file.

Bidri Hookah Bowl with Roses (c. 1650s)3Reasoned opinion

Every opinion, favourable or not, is reasoned in writing and verifiable.

Sweet Melancholy, Joseph-Marie Vien (1756)4Proportionality

The analyses undertaken are suited to the work, its value and what is at stake.

Saint Jerome and the Lion (From the former Church of St. Peter in Erfurt), Tilman Riemenschneider (c. 1495)5Mutual recognition

An OIMAP certificate is accepted by the 67 Member States.

The expert's independence

The expert is appointed by the Secretariat, never chosen by the declarant. They are drawn by lot within their specialty from among the available experts.

Before accepting, they declare in writing any conflict of interest: family tie, commercial relationship, holding works by the artist, earlier assignment on the same work. The declarant has 5 days to request their reasoned recusal.

Sports on a Frozen River, Aert van der Neer (ca. 1660)
Sports on a Frozen River, Aert van der Neer (ca. 1660)
Gathering among the Members of Office Censor-General (1700s)
Gathering among the Members of Office Censor-General (1700s)
Carnet (1863–1865)
Carnet (1863–1865)

A principle without exception

End-to-end traceability

Each file is a log: dates, participants, samples, laboratory results, documents consulted. Nothing is deleted; corrections are added without erasing.

This log is kept in the Registry for the whole life of the work. It makes it possible to reconstruct, years later, why a certificate was issued.

How the principle of reasoned opinion applies

  1. Finding

    The expert describes what they observe: materials, technique, signatures, condition.

  2. Comparison

    They compare the work with documented references: catalogues raisonnés, archives, autograph works.

  3. Analysis

    They interpret the laboratory results and indicate their limits.

  4. Conclusion

    They conclude with a degree of certainty: authentic, attributed, workshop, school, not authentic, undetermined.

The degrees of conclusion of an opinion

The five possible outcomes
ConclusionMeaningEffect
AuthenticThe work is by the hand of the stated artistCertificate issued
Attributed toStrong presumptions, without decisive proofCertificate with reasoned reservation
Workshop or schoolMade by the artist's circle or in the styleCertificate of a different nature
Not authenticThe evidence contradicts the attributionReasoned refusal, entered in the file
UndeterminedInsufficient evidence at this stageSupplements or analyses requested

How the principles came to be established

  1. Independence

    Ban on expertise paid by the seller in the founding States.

  2. Traceability

    Creation of the file log entered in the Registry.

  3. Reasoned opinion

    Directive No. 2019-07 makes the reasoned opinion mandatory.

  4. Recognition

    Extension of mutual recognition to the 67 Member States.

What an OIMAP certificate guarantees… and what it does not

Edge of the Woods Near L'Hermitage, Pontoise, Camille Pissarro (1879)

It guarantees

At the date of issue
  • A controlled, independent method
  • Sources and analyses open to consultation
  • A verifiable entry in the Registry

Solid documentary assurance.

The Departure of Saints Paula and Eustochium for the Holy Land, Giuseppe Bottani

It does not guarantee

In absolute terms
  • A market value
  • That no new fact will arise
  • The right to travel without a licence in every country

Hence the complementary acts: title, licence, approval.

Portrait of a Man, Gustave Caillebotte (1880)
Portrait of a Man, Gustave Caillebotte (1880)
Seal of Doge Michele Steno (reverse) (1400–1409)
Seal of Doge Michele Steno (reverse) (1400–1409)
The Four Seasons, Kano Tan’yū (1668)
The Four Seasons, Kano Tan’yū (1668)

A principle of caution

The Brook, Paul Cezanne (c. 1895–1900)
« An expert who is not sure must say so. Indetermination is not a failure: it is information. »
Dr. Amara N'Diaye, chair of the certification committee

Case study: a conflict of interest discovered

A recusal accepted

Situation

A collector files a case for a landscape attributed to a 19th-century painter. The appointed expert had, years earlier, advised on the sale of a neighbouring painting by the same artist.

Actions
  1. The collector reports the link within 5 days.
  2. The Secretariat checks the expert's declaration of interests.
  3. Another expert is drawn by lot and takes over the file.
Outcome

The timeframe is extended by two weeks; the certificate is issued with no possible challenge on independence.

Your rights in the procedure

Vocabulary of the principles

Challenge
Reasoned request to replace an expert.
File log
Dated history of all actions and documents in the file.
Degree of certainty
Level of conclusion expressed by the expert in their opinion.
Mutual recognition
Acceptance by each Member State of certificates issued by OIMAP.

Frequently asked questions

Can I choose my expert?

No. The expert is appointed by lot within their specialty, to guarantee independence.

Is the opinion confidential?

The file is confidential. Only the certificate, or its refusal entered in the Registry as the case may be, is enforceable against third parties.

What if the opinion is contested by a third party?

The third party may refer to the Arbitral Tribunal. The certificate remains valid until a decision.

Do the principles apply to digital certifications?

Yes. They rest on a paper certificate issued under the same conditions.

Contacts

Roman Ruins, Villa Pamfili, Hubert Robert (1774)
Roman Ruins, Villa Pamfili, Hubert Robert (1774)
Certification DepartmentParis — Headquarters+33 1 00 00 00 00certification@oimap.exampleMonday to Friday, 9 a.m. – 5 p.m.

Going further

Panel (c. 1780–1840)

Now discover how an application proceeds, from opening the file to issue.

See the process
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