In reply to Just found a Bulova 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.........
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:
Bulova produced the fabled 'Parking Meter' Bullhead Chronograph using the same movt, it was called the 14EFAD.