It stands for 40-T, one of Zenith's Observatory Chronometer movements...

Oct 28, 2014,14:27 PM
 

It could find out the following:


The Cal. 40-T is a 12" hand wound movement (thanks blomman for the pointer!) beating with 18.000 bph, produced between 1947 and 1963 in a quantity of 162.000 pieces. There were standard and chronometer-certified movements. It is Zenith's second-famous chronometer movement (after the slightly larger Cal. 135).

Here are a few images from a fellow Purist (of a non-chronometer 40T):






The particular watch in question is identical to one owned by famous watch journalist and historian Christian Pfeiffer-Belli. Assuming that all is still original and no parts (movement or dial) have been exchanged, chances are high that you own a true chronometer piece.

Hope this helps!

Best,
Magnus


 
This message has been edited by Ornatus-Mundi on 2014-10-29 06:39:09

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Old Zenith chronomete

 
 By: PakSu : October 25th, 2014-13:26
what is this printing in dial between centre and small cecond?...  

It stands for 40-T, one of Zenith's Observatory Chronometer movements...

 
 By: Ornatus-Mundi : October 28th, 2014-14:27
It could find out the following: The Cal. 40-T is a 12" hand wound movement (thanks blomman for the pointer!) beating with 18.000 bph, produced between 1947 and 1963 in a quantity of 162.000 pieces. There were standard and chronometer-certified movements....  

Zenith

 
 By: PakSu : October 30th, 2014-11:03
Great! Thanks!

A comparative pic between a chronometer-certified and a standard T-40...

 
 By: Ornatus-Mundi : November 4th, 2014-02:32
which I found on the web: (left, non-chronometer; right, chronometer version) Note the difference in finishing as well as in the balance wheel and the hairspring stud. Furthermore, the chronometer version is individually numbered also on the barrel bridge...