The eta 2892 appeared in 1975 and built till 1983 in 342123 examples
http://www.ranfft.de/cgi-bin/bidfun-db.cgi?10&ranfft&0&uswk&ETA_2892
Then appeared the eta 2892-2 in 1983 and built till 2000
http://www.ranfft.de/cgi-bin/bidfun-db.cgi?10&ranfft&0&uswk&ETA_2892_2
And finally in 2000 apperaed the 2892-a2 the latest variant of the eta 2892-a2 family
http://www.ranfft.de/cgi-bin/bidfun-db.cgi?10&ranfft&0&uswk&ETA_2892A2
The eta 2892 was derived from the caliber eterna 1504 which was one of the thinnest movements of its time.
Now see the pics I included and you will see why a vintage Omega movement is better than an eta 2892-2, I have taken for the comparison an Omega 1012 against a cal 1108 (an omega engraved eta 2892-2 with no improvements)
The Etachron accuracy regulation system is nowhere as good as a triovis or a swan neck regulation system, the jeweled pivot rotor winding system has always proven its superiority when it came to long term accuracy and durability against the ball rotor winding system.You can ask any watchmaker about that.
It is not because you use something mass produced that the watch will be good. The 7750 is maybe a widely used movement but it doesn't come to the toe of a lemania 5100 or a lemania 1350 in terms of finish, quality and durability.