The Number "1" Within the Omega Symbol on Constellation Movements


One query that has cropped up in watch fora regularly over the years is that of the presence of the number 1 inside the Omega logo on the train bridge of many mid-500 series Omega calibres.  Having emerged again on the Watchuneed forum, I am prompted to preserve for posterity the latest consensus on what that pesky little number means

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8 comments:

  1. Anonymous12:54 am

    Dear Mr. Guilfoyle,

    I'm surprised the meaning of those numbers are still a mystery, especially while every Omega repairer should know what they indicate. Calibers having a number in the Omega logo are prepaired for both flat and domed dials: 1 for (almost) flat, 2 for domed and 3 for high domed dials. For ordering parts carrying the hour, minute or second hand you need to indicate this number, otherwise you risk to receive replacements which are too short or too long.

    Upgrades of Omega calibers are indicated by a code starting with a 'T' and followed by a digit 1, 2 or 3.

    Best regards,
    Robbert H. A. ter Heide
    Maarssen, The Netherlands

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  2. Hi Robert, and thanks for your comments.

    I am aware that on earlier Omegas (at least in the 1950s) the numbers do indeed indicate the need to consider the height of the dial when ordering parts. I have seen reference to 1,2 and 3 on parts bulletins.

    However with Constellations, for example, with calibre 354 where both domed dials and pie pans were used there is no number stamped on the movement. Also for cal 561, for example, there does not appear any consistency that I can see with domed or pie pan dials - some domed dial original models had the number 1 stamped while others have not, and some piepans have while others have not.

    Perhaps we can continue this conversation by email - as I am very keen to get to the bottom of this issue.

    Click on the about me and you will see an email click through.

    Regards

    Desmond

    ReplyDelete
  3. Anonymous1:08 am

    Another thing I noticed is the little circle stamped on the rotor at some movements. As I could observe from studying photos of different movements, it seems that most 564 calibers do have circles wile 561s do not. I found also exceptions possibly because of changing the rotor in time. I also found pictures of some rotors more crude, without the beveling on the edges, but I tend to think those are non original parts installed later. I couldn't find a rule for calibers 551 and 751 however.

    Another interesting detail I observed in at the end of the swan neck spring at the regulator. At some movements there is a rounded end and at others the end is simple. I couldn't find a rule for this.

    By the way, thank you for your very informative site!

    Regards,
    Mihai

    ReplyDelete
    Replies
    1. Excellent observations Mihai.

      Yes, one explanation I heard was that the O indicated original factory rotor and not a replacement but that didnt make much sense overall.

      Change of some design aspects of the swan neck were cosmetic and came in later movements I believe.

      Very interesting little details
      .

      Regards

      Desmond

      Delete
  4. Anonymous1:16 pm

    Maybe after issuing the 564 they decided that the O should appear to indicate originality. I saw several 561 and 564 movement pictures and the exceptions where when there were also other color variations between the rotor and the other parts and this explains them by being changed later.

    Mihai

    ReplyDelete
    Replies
    1. Definitely a possible explanation worth following up

      Many thanks

      Desmond

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  5. Anonymous8:52 pm

    Was cal 561 used in the Constellation or only the earlier cal 551?

    ReplyDelete
    Replies
    1. Cal 561 was a chronometer grade movement as was calibre 551 and both were used in Constellations. These calibres are virtually identical, save the calibre 561 has a date mechanism, and they were both produced from 1959

      Cheers

      Desmond

      Delete