Pocket: Frodsham Pocket Chronometer

Discussion in 'Chronometers' started by CZHACK, Mar 4, 2010.

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  1. CZHACK

    CZHACK Registered User

    Apr 28, 2005
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    This pocket chronometer is a recent eBay purchase that was listed as made by Charles Frodsham but, I believe, is by his older brother John Frodsham. Any thoughts on manufacture date for the movement and recase? Comments welcome.
     

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  2. Dr. Jon

    Dr. Jon Registered User
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    I agree it's not Charles. The GE Frodsham Firm was at the Gracechurch location. This may have been by George's father who would be at least one generation ahead of Charles.

    The balance and layout look to be in the 1820-1840 period. I will look into it more in Mercer's book on the Frodshams, unless Frank M beats me to it.
     
  3. CZHACK

    CZHACK Registered User

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    Dr. Jon - Many thanks for initial information. What about John Frodsham? I understand he was Charles brother born 1885 and worked at Gracechurch St. before and after his partnership with Baker (Frodsham & Baker) in 1809. Given the low number, I thought dates might work. Any ideas on case production date? I assume it is a recent recase but at least since Sept. 2006 when it was sold by Jones-Horan. Then again, I understand many of these items were also recased in the late 1800s if in working use. Thanks again. Mike
     
  4. moskau

    moskau Registered User

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    #4 moskau, Mar 5, 2010
    Last edited: Mar 5, 2010
    Hello Mike!

    I am allmost sure, that this chronometer was made (or retailed) by John Frodsham (1785-1849 - The elder brother of Charles). He ran his business at Gracechurch/London (as you allready mentioned) from 1825 - 1842 with his son Henry-John and his Partner Mr. Baker. An earlier address of Frodsham/baker was possibly Kingsgate Street (1809-23). Unfortunatly i do not remember the sources of this informations...

    (I own a John Frodsham verge from 1828/29 with the same signature on the back-plate - i will attach a picture. Presuming a continous numbering system - it could help to date your chronometer roughly )


    I think the case of the chronometer was possibly made in the late 19th C. - (the somehow strange pendant looks a bit like a conversion from a former crown-pendant?)

    Harald
     

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  5. Dr. Jon

    Dr. Jon Registered User
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    I agree that John Frodsham is most likely the movement maker. Frodsham, Gracechurch St is the tradename from 1825 to 1854 which is the date most attributable to the movement.

    According to Mercer's book on the Frodshams John Frodsham was Charles's uncle. They were a large family and for the most part on good terms with each other often showing up at weddings and similar functions and bequeathing to each other in wills.

    All the Frodshams were well regarded.

    It's a very fine item.
     
  6. Frank Menez

    Frank Menez Registered User
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    #6 Frank Menez, Mar 5, 2010
    Last edited: Mar 5, 2010
    My Serial Number List shows that No. 196 was made by John frodsham 33 Gracechurch Street The following are the only S/N that I have for John Frodsham

    S/N 100 Circa 1808
    S/N 196 Circa
    S/N 331 Circa 1825

    These S/N were extracted from auction catalogues and I do not know if the dates are accurate.
     
  7. Frank Menez

    Frank Menez Registered User
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    The Frodshams by Vaudrey Mercer

    Page 242

    John Frodsham 1807-1808 12 Kingsgate Street

    John Frodsham 1809-1824 12 Kingsgate Street 1825-1834 33 Gracechurch Street.

    John Frodsham & Son 1834-37 33 Gracechurch Street
    1838-1853 31 Gracechurch Street
     
  8. Dr. Jon

    Dr. Jon Registered User
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    I think you have to assign Serial 196 to 1825. That is when John Frodsham moved there. Serial numbers are not necessarily in chronological order. One reason for this is lead time. It can be several months or more before a watch or chronometer has an assigned serial number and it is sold. It has to be engraved before it gets its final gilding and it may have to undergo final adjustment so some time can elapse. This may have been started before John moved but he had to have known they would be at Gracechurch St when the watch was to be delivered. That would have to be no earlier than 1825.
     
  9. CZHACK

    CZHACK Registered User

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    Harald - That is a fine looking watch. I would enjoy seing a full set of views. Thanks. Mike
     
  10. CZHACK

    CZHACK Registered User

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    Dr Jon and Frank - Many thanks for the information and your time.

    I was attracted to this item by its plain and functional look (unfortunately in a recase but a good workman like display case). It would be good to hear from anyone with information on display cases. I expect Harald is correct dating the case to later 1800s - say 1870-1880?

    Does anyone have information on how marine and pocket chronometers compared for accuracy? I have seen both fancy and plain balance cocks for good items by good makers, but it often seems as if they were making a minature version of the boxed chronometer as seen in this comparison of the Frodsham pocket and my Morris Tobias marine chronometer of about the same date:
     

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  11. moskau

    moskau Registered User

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    #11 moskau, Mar 6, 2010
    Last edited: Mar 6, 2010
    With pleasure!
    I bought it about a year ago. It is hallmarked London 1828/29 and in a quite nice condition.

    Concerning the accuracy question:
    I think, basically there should be not a big difference in the attainable accuracy between pocket and ship chronometers - (if the same technology is used throughout).
    One of the problems with pocket chronometers is propably, that they are carried around in different positions - and ship chronometers are normally kept standing, gimbal mounted in a box. So it is much easier to deal with the position problem.

    Harald
     

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  12. Dr. Jon

    Dr. Jon Registered User
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    Accuracy of box and pocket chronometers of that era is tricky because they did not measure or define it as we do today.

    I suspect that there was a lot of overlap between pocket and box chronometers in terms of accuracy. I define accuracy as the the uncertainty in time as a voyage progresses.

    By modern standards the Longitude act was not very demanding, a lot less stringent than US railroad requirements.

    A box chronometer would have had the advantage noted being in one position as well as a larger and more energetic balance wheel and probably a higher "Q" factor. Q is a measure of the precision of the time standard and its proportional to the ratio of energy in the balance to the loss per cycle.

    On the other hand it would have seen more severe temperature changes than a pocket chronometer carried in an inside pocket and might have been subject to less ever shocks in extreme conditions in a pocket.

    To meet the Longitude act a chronometer could have an uncertainty of over 10 seconds per root day. (The average uncertainty due to this error grows with the square root of time.) According to a maker's trade paper in a chronometer I own, he won the trial prize in 1857 with this error at a bit under 2 seconds per day and by the late 1800's it was a a few tenths of a second.

    The Swiss had differing standards for box, "torpedo boat", and pocket chronometers for first class certificates. If you look at the rates of the competitors as published, a lot of pocket chronometers would have placed high on the list had they been entered as box chronometers.

    If you want to try yours, compare it to a standard twice a day for about 10 days. Fit the rate to a straight line and compute the standard deviation of all the differences, there should be about 20. If you get a standard deviation under five seconds it's probably doing as well as it ever did. At ten seconds its doing well enough that I would not "mess" with it.
     
  13. CZHACK

    CZHACK Registered User

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    Dr Jon - Many thanks for the information and I will give it a try for accuracy (maybe time the pocket and marine chronometer in my own mini time trial).

    Harald - Not sure which I like more (the case or movement) and a quality item in great condition.

    Mike
     

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