This means that the case is gold-plated, 20 microns thick and made by Omega.
At the end of the 1970's Omega was making dozens of different models every year. Many of them are not listed in their online database.
This is the closest one I could find:
https://www.omegawatches.com/watch-omega-geneve-omega-md-166-0117
Note that the "Geneve" and "DeVille" names were used on watches in some countries and not in others.
Hope this helps,
gatorcpa
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