Maybe. These tolerances are for testing done under controlled conditions in a shop, and using a timing machine that is only measuring over a short period of time. So the first thing to keep in mind is that the tolerance of -1 to +16 is an average, and it's only measured over 3 positions. The numbers that make up this average are given equal weight during testing, so it assumes that the watch will spend equal time in all those positions. So this does not always reflect what you see on your wrist.
So obviously your watch can be positioned in many more positions than just 3 when you are wearing it, so it's possible that positions that are not being measured may have an error that is quite large, and if your watch spends significant time in one of those positions, that will affect the average that you see on the wrist. This is why I always test every watch I service over 6 positions, no matter if the brand says it should be tested for just 3 or 5. The watch can be worn in an infinite number of positions when worn, but 6 will give the watchmaker a very good idea of how the watch will perform in my experience.
Also there is another set of tolerances behind that average number, and those are what I mentioned above - the Delta and the isochronism error.
So on the 321, Omega allows the Delta (the difference between the fastest and slowest position measured) to be as much as 20 seconds when measured at full wind. This means that if one position is say zero gain or loss, that the other two can be -10 and +10, and all readings would be within tolerances. But it could also mean that the average is on the high end at +15, and that means the individual readings that make up that average could be something like 5, 10, and 25. So in one particular position the watch will run at +25, so again if it happens to spend a lot of time in that position, it will run faster than the allowed average, but would still be in tolerance.
Note that Omega also has tolerances at 24 hours after full wind, and there the Delta is allowed to be as much as 30 seconds. So as the mainspring winds down, they allow for the accuracy to drift. So the first example above I gave where the average is zero, now the three readings could be 0, -15, and +15.
If you take all this into consideration, you can see that there could easily be a watch that is fully within tolerances, and running very close to +30 per day. Of course if yours runs consistently +30, I would look into getting it regulated if that is a concern.
I know you had the watch serviced at STS, but I don't know if they gave you any timing data. I always include this in the documentation that I provide, and I also let the customers know what positions run faster or slower so they know what resting positions to use without having to spend the time figuring that out through experimentation. I base this on real world tests, not the timing machine results, because I test the watches by letting them sit in each of the 6 positions for 24 hours each, and note the gain or loss each day.
Hope this helps.
Cheers, Al
