Buren were partners with Heuer and Breitling in the development of the Chrono-Matics and made the base automatic movement. By 1969 after they were taken over by Hamilton they were making all the Hamiltons too. Buren signed chrono-matics are very scarce, I think this is only the second photo I have seen of one.
Jeff Stein did a good write-up of how these relationships worked
http://www.onthedash.com/docs/Project99.html
I am wearing the Buren's sister today, although the photo was taken in summer.
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