How accurate is your watch?

Contrôle Officiel Suisse des Chronomètres is a Swiss based organisation that tests Swiss (only) chronometers, or watches (from the Greek – perhaps – to write, or meter, time, chrono). If you’ve got a COSC certified watch, eg a Rolex, this means that at some stage in it’s early life (long before it was shipped to a retailer and then bought by you) it was tested and it met the COSC standard.

It doesn’t mean it’s going to be accurate today, tomorrow or next week.

There are plenty of arguments that COSC certification is just marketing spin, it certainly adds to the cost of the watch (and probably a lot more than the cost of testing).

But here’s the thing: mechanical watches aren’t accurate. COSC says that over the first 10 days of testing the watch must not lose, on average, more than 4 seconds a day or gain more than 6 seconds a day. So in any given day, a mechanical watch needs to be accurate to 0.007% or better (6 seconds a day, 86,400 seconds in a day).

Doesn’t sound like much, does it? 0.007% accuracy would seem pretty good …. until you set your $5,000 watch to the time pips on ABC radio tomorrow morning at 8am, or to the talking clock, and then you glance lovingly at the dial three days later at the sweep hand is almost 20 seconds fast. Piece of junk? Nope, it’s within tolerances. So what, I paid a lot of money, I want accurate!

Want accurate? Configure your iPhone to sync with the phone network or buy something like a Timex Ironman. $100 or so. My Ironman is 5 or 6 years old and until about 12 months ago it was my beater, my wear anywhere watch, I don’t care what happens to it (it replaced a Russian pilot / chrono that broke once too often and couldn’t be repaired; motto: not all beaters can take a beating). It’s been cycling, swimming – pool & ocean, skiing, and motor bike riding (my goodness, I lead a busy life).  Not a scratch on it (plastic case helps) and keeps great time. It’s not a COSC certified quartz – they’ve got to be better than +/-0.07 seconds/day, or 0.00008% accuracy – but I reckon it’s pretty accurate.

Quartz doesn’t really have the romance of mechanical. I get together once a month with a bunch of Melbourne watchnerds (use the #watchnerd to see what we chat about on Twitter) to have a couple of drinks and discuss all things horological. I have a feeling if it was a group of guys chatting about quartz watches it wouldn’t be all that interesting. Yes, I know the prospect of having a drink with a group of watchnerds probably isn’t all that exciting for everyone, but I enjoy it.

Mechanical watches are little machines you strap to your wrist, they have romance, they’re built to last (I have a couple of watches from the 1940’s in my collection – and they keep good time), they’re the sort of thing that gets handed down a generation (I can’t see too many Grandfathers passing on their Timex Ironmans), they make noise (tic, toc – what sort of noise were you expecting?), and well, I like them.

So I’m going to run an accuracy test over the next week on a few of my watches. In the line up are: A Rolex GMT-II, about 10 years old, first sold in Hong Kong in Feb 2002, and recently serviced; A Bell & Ross BR 01-92, 4 years old, advertised as “military spec” (whatever that means), never serviced. A Graham ChronoFighter Oversize GMT with Big Date (the watch is bigger than the name, but only just), 2 years old, it had a few issues ‘out of the box’ but fine since it was attended to by the local Authorised Dealer just after I bought it, and a Longines triple date moon phase chronograph (I like those long descriptive names), 18 months old. All four are Swiss.

There’s a Seiko Diver, a 7S36-04E4 if you must know, I bought it new for about $100, maybe 2 years ago. This is one of my beaters, and I’m planning to take it (and maybe one other watch) on my summer beach holiday.

Every pack needs a Joker, and this bunch has two for good measure … an homage to trhe Rolex GMT, homage being Watch French for “as close to a copy as we can get without getting in trouble”. Not branded, supposed to be good to 200m water resistance (I doubt it), this is my current sports beater. Heading out on the bike or for a run, this is #womw (what’s on my wrist). And a recent addition, a 1970’s (I think) Russian Poljot chronograph. Sorry watchnerds, there are no markings on the dial or case back to indicate model or movement. The case looks like it’s been refinished (how else does a 40 year old watch not have a single scratch?) but I have no idea about the movement, or when it was last serviced (if ever).

The rules …. each watch to be set on a full minute, ideally a 5 minute (easier to be accurate); each gets worn for one day this week; watches go on the winder when not being worn, other than Bell&Ross (it doesn’t fit) and Poljot (it’s a manual wind watch, so the winder isn’t going to do it much good); accuracy to be check each evening and daily results posted on Twitter; full report here in about a week.

Questions? Suggestions?


This entry was posted in Uncategorized. Bookmark the permalink.

2 Responses to How accurate is your watch?

  1. Bob Meade says:

    I gather that the Bell & Ross and the Poljot will sit in the draw/on the shelf when not being worn? If so, suggest change position daily to face up, face down, crown up, crown down, face down, crown up, crown down.

    You’ve outlined a pretty good test.

  2. Bob Meade says:

    Oops. eliminate the first turn of “face down” in that sequence.

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s