Move the pendulum and look to see if there is the OXG mark. If so, then it's the rare US version. If not, it was made in Europe.
All Cal. 560 movements should have “OXG”. These are 17 jewel movements that were specifically made for export to the USA. This was done because of extra customs duties on watches with more than 17 jewels at that time.
I have never believed the production figure of 3,000 from Omega on the Cal. 550/560 production. There were a lot of them shipped directly to the U.S. importer. Perhaps that figure refers to the models actually cased in Switzerland, like the one above?
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