A certificate of accuracy is an attestation following a chronometer certification, issued by an accredited testing authority.
From the Swiss testing authority COSC two types certificates are issued
The great certificate , which contains all test data or the test result. Here the individual rate deviations and the medium rates under the relevant test conditions are listed.
The small certificate does not contain any rate values and is understood merely as a certificate that states that the movement has met the required standards at the time of the audit.