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17, 30
Posted July 22, 2018 - 4:07pm

Just found a Bulova Ambassador with a caliber 12EBACD micro-rotor (Buren 1322), does anybody have any info about it ?
I am discussing purchase, looks very good, should be 1965, no code on the back but on the movement a M5



Reverend Rob
Posted July 23, 2018 - 12:19am

In reply to by Proby01

I have one of these, a 1966 solid gold bezel version, and I will say that micro rotors in general require more movement than regular automatics. 

This is a well engineered movement and definitely under-appreciated by collectors.

A friend of mine has a Patek Micro Rotor watch, and he says the solid gold rotor makes a difference in winding efficiency. So all we have to do is make a solid gold rotor for these.........

Reverend Rob
Posted July 23, 2018 - 12:17am

Hamilton so loved the Buren Micro Rotor they based the world's first Automatic Chronograph on it, in conjunction with Breitling (March 3, 1969), Heuer, and Dubois-Depraz, and thus the Chronomatic (Calibre 11) was born. Hamilton acquired Buren in 1966. 

Buren patented the Micro Rotor winding system, called 'Planetary Rotor', in 1954, but it did not go into production until 1957.

Just a few of the models using the Chronomatic Cal. 11:

Breitling Chronomatic

Breitling Chronomat

Heuer Autavia

Bulova produced the fabled 'Parking Meter' Bullhead Chronograph using the same movt, it was called the 14EFAD.

Posted December 19, 2020 - 12:15pm

12EBACD M8 17-Jewels: