# Accuracy of your JLC



## dero (Nov 4, 2011)

I bought my Master Hometime just over a month ago and I have to say that this watch is incredibly accurate.

After a month, worn daily, it's -1 seconds off atomic time. Through regular checking, it was dead onto atomic time for about the first 10 days. The second 10 days it was about +1 second fast and now the final 10 days of the first month of ownership it's been about -1 second. Am I simply lucky or is the Master 1000 Hours Control testing and regulation really make these watches so accurate?

I'm incredibly happy with this watch. It's beautiful, accurate, comfortable and the 975H movement looks superb.


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## lvt (Sep 15, 2009)

dero said:


> Am I simply lucky or is the Master 1000 Hours Control testing and regulation really make these watches so accurate?


You are lucky, accuracy is a relative value, it will vary with time depending on the movement's condition and your wearing habit.


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## The1 (Feb 1, 2012)

and state of wind. mine gets faster if i let the wind go low.


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## st8edge (Dec 9, 2008)

My MC GMT Diver .44 is amazingly accurate. I have not adjusted it for over a month and only check it against my atomic watch and am very happy with it. This watch is a little hard to compare because it does not have a second hand and has a disk which shows it is operating but it appears to be very accurate.


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## drewmcd24 (Mar 9, 2010)

I wouldn't say it's all luck. I think the major benefit of JLC's 1000 hour testing phase is that you get a watch that's regulated carefully in many different positions and monitored and adjusted as needed throughout the process. So once it's on your wrist you're getting a finely tuned machine. If you buy something from a manufacturer that doesn't spend so much time testing and monitoring the watch before delivery, you're probably going to get something within a wider range of accuracy. In other words, it could be dead on or it could be a few seconds fast or slow per day. The acceptable window is wider.

I don't really have an easy way of testing my JLC because it has no second hand, but it's been very accurate in the month and a half since I bought it.


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## BA211 (Apr 1, 2011)

None of mine have second hands, but I do find them to be very accurate. The benefit of the testing I am sure.


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## Jebhut (Apr 12, 2010)

dero said:


> I bought my Master Hometime just over a month ago and I have to say that this watch is incredibly accurate.
> 
> After a month, worn daily, it's -1 seconds off atomic time. Through regular checking, it was dead onto atomic time for about the first 10 days. The second 10 days it was about +1 second fast and now the final 10 days of the first month of ownership it's been about -1 second. Am I simply lucky or is the Master 1000 Hours Control testing and regulation really make these watches so accurate?
> 
> I'm incredibly happy with this watch. It's beautiful, accurate, comfortable and the 975H movement looks superb.


JLC makes some of the finest movements in the industry...the testing is more about dependability from my understanding...and accuracy. Accuracy is detrmined by its consistency, whether +1 or +8 a day. (Can always be easily 'regulated' if it's accurate, right?)

Yours is ridiculous - assume you're aware very few watches maintain a 'dead on' daily rate...but as Breitling once told me, it's better to be a bit fast new, as it'll slow after a while. Had a JLC running 8 fast a day new...JLC said it was fine, not to mess with it...my present MCDC runs +3. Of course one good whack, and it might not be...the quality of the movement is not measured by its daily rate...wear habits, even temperature affects that.


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## lvt (Sep 15, 2009)

drewmcd24 said:


> I wouldn't say it's all luck. I think the major benefit of JLC's 1000 hour testing phase is that you get a watch that's regulated carefully in many different positions and monitored and adjusted as needed throughout the process. So once it's on your wrist you're getting a finely tuned machine. If you buy something from a manufacturer that doesn't spend so much time testing and monitoring the watch before delivery, you're probably going to get something within a wider range of accuracy. In other words, it could be dead on or it could be a few seconds fast or slow per day. The acceptable window is wider.
> 
> I don't really have an easy way of testing my JLC because it has no second hand, but it's been very accurate in the month and a half since I bought it.


The movement is tested in different positions for 1000 hours but it's automatically would by robots so it always has an optimal power reserve (same way like COSC but COSC only tests the movements for 360 hours), being mechanical movement, the movement's isochronism could be affected by the winding state (you wear your watch everyday 24/24 => optimal, you wear it sparingly like 8-12 hours per day => winding state varies).


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## dero (Nov 4, 2011)

Yeah I realise that it's ridiculously accurate. This was the reason why I posted. I was surprised to say the least that at week 6 I was -1 second off atomic time from when I set it on date of purchase. Today it's sitting at -4 seconds off atomic time and I've yet to touch it other than to throw a few winds every second morning. I found it amazing and thought that this was something perhaps not experienced generally by other watches that have undergone the 1000 hours testing and regulation so thought I'd ask the community.

It's worn approximately 11-12 hours every day.


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## drewmcd24 (Mar 9, 2010)

lvt said:


> The movement is tested in different positions for 1000 hours but it's automatically would by robots so it always has an optimal power reserve (same way like COSC but COSC only tests the movements for 360 hours), being mechanical movement, the movement's isochronism could be affected by the winding state (you wear your watch everyday 24/24 => optimal, you wear it sparingly like 8-12 hours per day => winding state varies).


The 1,000 hour control process is much more extensive than that. They test the complete watch, not just the movement, in a fully wound state and simulating the conditions of normal use.

From The Purists:



> The first thing is that the Master Control 1000 hours (COSC 360 hours) test is carried out only when the watch is fully assembled, including casing, hands and dial, not just the movement (COSC, movement only):
> 
> Accuracy must be within the range of -1 to +6 seconds per day (COSC -4/+6 for Gents and -5/+8s for Ladies)
> 
> ...


http://www.network54.com/Forum/234648/message/1052748253/The+Master+Control+1000+Hours+test


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## lvt (Sep 15, 2009)

drewmcd24 said:


> The 1,000 hour control process is much more extensive than that. They test the complete watch, not just the movement, in a fully wound state and simulating the conditions of normal use.


Of course COSC doesn't test the complete watch because they don't even know which watch will uses this or that movement, in fact they only test Swiss made movements that came from different manufacturers, so tests like water-resistance or 20,000 simulated shocks are impractical, and temperature test of 4-40°C instead of 8-38°C doesn't impress me either.

And as they test millions of movements per year they only can test the most significant technical aspects, the most importance -- accuracy -- is comparable for both COSC and JLC because watchmakers usually regulate the movement sothat they run slightly fast.

Seiko doesn't test their movements for 1000 hours but their watches are regulated to run better than COSC (-4/+5).


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## budhudson (Mar 17, 2009)

Interesting this one

Just checked my set and get the following -

Master Control Hometime +2 sec
Master Compressor Dualmatic + 2 sec
Reverso Squadra + 4 sec
Reverso Duo +5 sec

These are all against computer clock that i set them against

What is worrying (read pleasing) is that i did this before xmas


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## Ados (Feb 4, 2012)

Here is how my Master Calendar has performed from the 19 Sep 2011 to 4 Feb 2012:










Last period of measuring it gained an average of just 0.06 sec/day

As you can see I had my watch adjusted in September. I ware my watch every day. Except from the 9 Jan to 15 Jan as the watch was laying constant on the crystal.


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## knebo (Jun 13, 2017)

I just bought a JLC Master Geographic (142.8.92) at an auction -- originally sold in 2001 and I have no info about the service history. 
Over the first 24 hours it's running very well. 
--> at -2 s/d with crown up
--> at +2 s/d worn. 
So with some smart positioning over night, I should be able to keep it spot on. I hope it keeps running like this. I'll report if anything changes.


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## playitleo42 (Apr 12, 2016)

I have a Geophysic True Second. On the wrist it is about -0.5/day. I wear to work and change when I get home most evenings. Stored crown left/12 down it gains about +2 sec per day. In my wear pattern I am about +0.8 sec per day average as I usually don’t wear on weekend and runs a bit fast when not fully wound.


Sent from my iPhone using Tapatalk


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## Porsche993 (Jan 6, 2017)

playitleo42 said:


> I have a Geophysic True Second. On the wrist it is about -0.5/day. I wear to work and change when I get home most evenings. Stored crown left/12 down it gains about +2 sec per day. In my wear pattern I am about +0.8 sec per day average as I usually don't wear on weekend and runs a bit fast when not fully wound.
> 
> Sent from my iPhone using Tapatalk


Same as mine. Definitely likes to be kept fully wound so I keep this one on an automatic winder.


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## American Jedi (May 27, 2017)

I have a DSC that is +1 -1 a day. I also bought 2 NSAs for my son and I. His runs +-3s a day, but mine after JLC service runs +6?
Guess it needs to be regulated?


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