momosono
·I don't believe Omega will provide a COSC certificate for a 40+ year old watch.
COSC does not sell them to individuals. From the COSC web site:
"What information can the buyer of a certified chronometer watch obtain from the COSC ?
None. The COSC is the repository of analytical results that belong to its customers (the watch brands). It does not have the authority to disclose information to anyone other than the legitimate owners of those results. The buyer should contact the head office of the brand to which the chronometer belongs."
I doubt there is a way to get this certificate, even if one exists.
The way I understand it (edit: especially reading the French version of their site) you can ask a copy from COSC and they'll issue one only, which will be marked duplicata. Also from their website
What if a COSC certificate has been lost ?
A COSC certificate is considered be a valuable document. The COSC is authorised to issue only one copy of a certificate, bearing the word ‘duplicate’. In case of loss of a duplicate, the only way to obtain a new document is to subject the watch to a new control. In this event, only the brand may request this service. The head office of the brand that has marketed the chronometer must therefore be contacted directly.
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