# System for recording movement thickness?

#### tick talk

##### Registered User
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

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

#### agemo

##### Registered User
Hi,
I have this if it can help.

Amicalement GG

#### eri231

##### Registered User
The thickness of a movement is expressed in twelfths of a line. so 15/12 is (a line) 2.256 divided by 12 = 0.188 multiplied by 15 = 2.82 mm
hope this help regards enrico

#### tick talk

##### Registered User
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?

Last edited:

#### gmorse

NAWCC Member
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

##### Registered User
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

##### Registered User
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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