Foo2rama
··Nowhere near as grumpy as he used to be...In Switzerland? I thought Seiko used some other horological body.
This being said, "officially certified chronometer" or even having chronometer on the dial is defined by ISO 3159 first codified in 1976, and the current revision is dated 2009 and was recertifed in 2015 with no changes and is to be reviewed in 2020.
So date of the watch is needed on the piece in question. That being said Seiko in 1976 could have had an inhouse test for ISO3159 and legally labeled the watch that way. Currently afiak there is a German Body that can certify a watch as a Chronometer and the watch would not go through COSC.

