2016 sounds close enough. The long-running forum thread for FOIS Roll Call might be the publicly-available resource for this... if so inclined, you can create a color-coded heatmap of the self-reported LE # by the year the incoming / new owner posts were written in that thread. Color mapped either by strata of 1,000 or 1,500.
Anecdotally: I purchased my FOIS new-in-box from a US grey dealer in November 2017, who had sourced it from an AD in Sweden. The LE number was 7854.
When I first got into the hobby around the mid-2000's, we used to be able to email Omega's general customer service team in Bienne and ask them directly. I remember emailing them the serial number of a 2254 (my first nice watch!), inquiring on its date of manufacture, and they replied the same day with the month & year it was made.
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