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A Russian MMX or I should say 6MX might be 4/10 to 1 second or so for a really 
good one and you need to compensate that at the rate of 1/10 second per day 
per degree centigrade. The Hamilton model 21 might be as good as 1/4 second 
per day with no compensation for temp. The balance wheel is designed 
differently and uses a metal peculiar to Hamilton.

The really important thing is that the rate for the Hamilton is almost 
constant and the MMX varies from day to day. That is the biggest difference 
between them. If you clean them and adjust them equally the Hamilton is the 
better rate keeper.
Robert Gainer

>
> From: Red 
> Date: 2006/05/15 Mon PM 08:48:25 EDT
> To: NAVIGATION-L@LISTSERV.WEBKAHUNA.COM
> Subject: Re: mechanical chronometers
>
> Thank you, Robert. What are the typical figures for accuracy and for the
> stability of the rate in a marine chronometer? I know the rate of mechanical
> wristwatch chronometers can be adjusted by varying the position they are kept
> in, i.e. stem up/down, 12/6 up, etc. For those who take their watches off at
> night, this can be used to regulate the watch often to a difference of +-5
> seconds per day without the need to open them.
>  I have over the years sometimes marked down the rates for various watches and,
> aside from the battery powered ones shifting as the battery was allowed to age,
> I can't really say I've noticed much fluctuation in them.
>

   

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