Omega doesn't disclose anything about when a watch movement was constructed, and to my knowledge, never has. All you know for sure is that a movement was constructed prior to the shipment date, and if a chronometer, prior to the earlier testing date.
Made:
For the 100,000, they were constructed prior to the date of testing. Exactly when, we don't know. I have never seen discussion of how long after manufacture movements were sent for testing.
Tested:
An independent testing group issued the chronometer certificates with the actual date testing was completed. Recall that chronometer testing takes place on uncased movements, not yet assembled in to a watch. These testing completed dates are the dates Omega is quoting, and ranged from October 1964 to February 1966, if I understand it correctly.
Shipped:
Omega provides, for any watch, an extract from the archives, of the date the watch was shipped from Bienne to the sales agent. If the information in the serial number charts are to be believed, the earliest date a movement with a 24,000,000 serial number (the 100,000 was in this range) was shipped was not until 1966.
Assume this is true, and assume Omega used manufactured and tested movements in serial number order. There was a delay of at least 15 months (October 1964 until January 1966) after testing until the first of the 100,000 were used. The time since actual manufacture would be greater by whatever (unknown) gap there was between manufacture and testing.