[silisili]

I'd say you got a lucky one. From Hamilton's own site -

> Most watches that do not have a chronometer certificate have an average course deviation of -10/+15 seconds per day. To be called a Chronometer, the mechanical watch mechanism must have an average course deviation of -4/+6 seconds per day.

[WrongAssumption]

That’s a min/max daily range that is influenced by factors such as movement, angle, temperature and magnetism. They generally do not hit the min max and average out quite a bit day to day.