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I've been bidding on an old salvaged Seiko QM-10 Marine Chronometer on the 'Bay... The price just keeps going up and up... what do I really want ?

Ah Ha, 'there's the rub' as Hamlet liked to say, what I want is a highly accurate time piece to serve as a reference and for the 4 figure price that the QM-10 currently is at I can probably get a caesium ion frequency reference and could certainly buy at least 2 fully functional rubidium frequency references....

Of course, I'd like a QM-10 too, just to see how accurate it really is....

By the way those of you who remember my musings about wrist sized caesium ion frequency references, they are now in their 3rd generation of prototypes and it looks as though ere long those wizards at the NIST will have perfected the technology to produce reliable cesium / caesium ion frequency references small enough to be worn as a wrist instrument....

Now that's a time piece I really want !
 

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Well, you can now get Dick Tracy style wrist radios -- except they can talk to anyone with a phone - a distinct advantage. This due to a market existing for such which drives the technology to satisfy the market. Where is the market for portable atomic clocks?

BTW, search the forum... one of the members has reported on the accuracy of a Seiko like you are looking for...
 

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I'd say any two devices that need to stay in sync - timebases for the sort of NP incomplete codes that use paired mathematically random (ie. incompressible) number streams switched in sync (or at least within tolerance) by two identical timebases. What value unbreakable realtime voice comunications? As it stands, given a while even PGP is probably completely insecure. PDP has seen to that. The only way to make a code secure is to have no regularities at all. For that you need paired random numbers.
 

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PDP?? BTW, PGP allows use of a variety of algorithms... OTPs are secure, but what does this have to do with sharecroppers in Alabama?
 

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JulianS,

That Seiko QM-10 Marine Chronometer looks nice.
However, it is similar to the QC-951 (Seiko Crystal
chronometer) and will have similar accuracy. Seiko
specifies the accuracy as +/- 0.2 s/day, though a
typical example may perform better in your environment.
You can read more in this excellent review article: <http://www.network54.com/Forum/78440/thread/1198952723/Seiko+Quartz+history+and+the+Crystal+Chronometer+(many+pics)>

Given the price of the QM-10, you might shop for
the QC-951, which (in my opinion) is historically
more significant. I expect the QC-951 should sell
for much less.

Talk of high stability frequency references is
entertaining, but using one as a basis for time
keeping requires a high performance way to set
and read the time. Otherwise you could use up
a whole life time waiting to measure a human
readable drift.

Thanks for pointing out that Marine Chronometer.
It is nice see these time pieces drawing
attention in the market.

rationaltime
 

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JulianS,

That Seiko QM-10 Marine Chronometer looks nice.
However, it is similar to the QC-951 (Seiko Crystal
chronometer) and will have similar accuracy. Seiko
specifies the accuracy as +/- 0.2 s/day, though a
typical example may perform better in your environment.
You can read more in this excellent review article: <http://www.network54.com/Forum/78440/thread/1198952723/Seiko+Quartz+history+and+the+Crystal+Chronometer+(many+pics)>

Given the price of the QM-10, you might shop for
the QC-951, which (in my opinion) is historically
more significant. I expect the QC-951 should sell
for much less.


Talk of high stability frequency references is
entertaining, but using one as a basis for time
keeping requires a high performance way to set
and read the time. Otherwise you could use up
a whole life time waiting to measure a human
readable drift.

Thanks for pointing out that Marine Chronometer.
It is nice see these time pieces drawing
attention in the market.

rationaltime
Here are some pictures of my Seiko QM-10. Keeps very good and consistant accuracy -- something around +7 seconds per year. Mine was purchased as new in Feb 2000 from a dealer in Marine Chronometers (mostly restored Hamilton and Parker & Frodsham mechanical chronometers). My date of manufacture is from 1991 according to the certificate from Seiko. The quartz crystal vibrates at 4.19 mHz and the seconds hand steps in 1/2 second increments.









 

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Moderator German Watches Forum
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Omegaman,

Wow, you bought a new one. Thank you for posting
the information.

Even with its 6.27 KHz crystal, the QC-951 "average
daily rate" from 1963 is just 2x your new QM-10. I
do not have an inspection sheet to see whether the
QC-951 production inspection values are related in
a similar way to the specification. With the small
sigma you show and reasonable environmental control,
the navigator could reduce the time keeping error to
less than the time reading error. (Of course, in the
21st century most navigators would be using
electronic navigation.)

As you likely know the QC-951 operates on 3V, and
moves the second hand in approximately continuous
fashion.

Thanks,
rationaltime
 
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