System for recording movement thickness?

tick talk

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Sep 16, 2008
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I've come across reference to a vintage Swiss wrist watch movement of the 1930s described as size 10 (lignes) 15/12. I've seen this before with Swiss pocket watch movements, and vaguely recall the fractional number was a reference to hauteur/thickness, proportion of thickness to width, or some such. Can someone please enlighten me on this system?
 

tick talk

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Here is a page from the V&C photo reference archives with many examples, both pocket and wrist.
IMG_1599.JPG
 

agemo

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Apr 5, 2011
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Hi,
I have this if it can help.

table_douzièmes.jpg

Amicalement GG
 

tick talk

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Brilliant Enrico, that helps for those written as x/12. Can you tell me the meaning of those other fractional values, ie, 20/22, 20/21and 19/19?
 
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gmorse

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Hi Enrico,

That's interesting, the Swiss using 1/144 of a French inch (pouce) for this measurement; the Lancashire gauge also measured pillar heights in increments of 1/144 of an English inch, although it started at 1/8" as the zero point.

Regards,

Graham
 

eri231

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I really have no idea of the other fractions / 21/22. Even 19/19 would not make sense when referring to a measurement. For the mainsprings it was different measurement methods but for the movements I only know the lines and fractions in twelfths. For the glasses of the cases there are measures in / 8 and / 16
regards enrico
 

tick talk

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Philip gave me the answer to the other fractions, nothing to do with thickness. Its the relative size of front and back movement plates! Now I can rest easy, have learned something new today.
 

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Rockford's early high grade movements by Greg Frauenhoff