IF the glass is really chamfered sapphire, then that is probably the most expensive part of the entire watch....But I am a bit doubtful they really mean 'sapphire'; it's likely only PR talk.
9F is just superb....The older Citizen Chronomaster (still findable on sales sites here and there, but slowly dissappearing) is more accurate, and has a perpetual calendar window - very handy in everyday life!
But the 9F has the spring to counter seconds hand backlash, a sealed movement, a two step seconds hand motion (invisible to the eye) and a super fast date change. It also looks classy 🤗
I don't know how the battery driven Citizen Chronomasters are compensated for time keeping, but the 9F is just simplicity iteself: the quartz oscillator's abberrations and drifting is recorded/calibrated and fed into a chip in each movement so that these can be 'zeroed out'.
And most important (for me anyway!) : there are parts for 9F repair for decades into the future... I am not so sure that will be the case if a damaged Chronomaster needs work 15 years from now...
It is news to the people at Seiko Japan because:
For many, many years, their own PR kits handed out to us at Baselworld press meetings supplied the +/- 5 seconds rate per year for the 9F for almost two decades. This is why you will see it stated on many older websites/blogs/articles if you look around the net.
Now, officially online, they talk about +/- 10 seconds a year, which seems to be a misnomer of their PR department or they don't know what they want to really say 🙃. Or they are being very clever...
In watchmaking jargon, a watch with +/- 5 seconds per year rating means it can (will) run in a range between 5 seconds fast to 5 seconds slow - therefore the watch has a rate spread of 10 seconds a year.
However, IF the +/- is being used as general PR commment, (non-technical horologically) then the latter 'spread' is inferred (i.e. the +/- sign means equal to 'about' 10 seconds a year.) They have lost something in translation here...Or they are making it deliberately murky, to supply buyers a reason for purchasing a higher priced model, with no more accuracy than the base 9F supplies because it has a star now on the dial...If they really meant technically +/- 10 seconds a year, this is a rate spread of 20 seconds per year, which is rather mediocre for a quartz wristwatch in this price class, and nothing to be proud of!
I don't know exactly when this 'star' system on the dial was implemented for these 'more accurate' 9F based models, but I have three watches with the 9F, none of which has a 'star' on the dial, and the oldest, a Seiko Astron Anniversary model (from 2002? 2003?) still keeps time at +/- 3 seconds a year with battery and gasket change regularly done.. The other two 9F movements, (2008? 2010?) - also lacking the star), have never gone outside the 5 seconds fast/5 seconds slow - it is uncanny how good the 9F powerhouse is.
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