I need a balance staff for a Hamilton 670 Traffic Special. I know it's a Cortebert swiss movement, but I can't seem to find what the balance staff it uses. I thought it was a Cortebert 736 movement and ordered a balance staff from Italy. I received it today and it's not the correct staff. Does anyone know what staff it takes or where to find one? Thanks for the help.

What is the diameter (in lignes or millimeters if possible) of the movement John and also the thickness without the dial? I think the Hamilton 670 "Traffic Special" was smaller then the standard American 16 size.

A shot of the movement and also an under dial shot would be good to identify the Cortebert calibre as well as the measurements I spoke of above.

The movement measures 41.65mm across and I believe it's a 18 1/2 lignes. Hope this helps.

I just talked to a friend and he said the 670's were a Cortebert 437 movement. He said the staffs came in two versions. The collets were different. .8mm or .9mm size.

Your friends comments are interesting, as I did not know they even made a Calibre 437???

I had another 670 that had the number 736 stamped under the balance. I would be interested what your thoughts are?

I have my thoughts on what it may be, but could you give me the "Thickness or Height" of the movement in millimeters please, as that might possibly give a better insight?

Can you also recheck that dial measurement, which position are you measuring on the dial, can you also upload a photo of the back of the movement and dial plate without the dial?

It measures 4.70mm thick and I'll attach a pic of the plate. Let me know if this helps.

With that setting & winding Mechanism it's looks to be a Unitas movement John, any of the Cortebert's I have seen have a different setting mechanism.

Did not Unitas take over Cortebert, the only size Cortebert I have come across that is 4.70mm high is a 16 Lignes?

The Unitas movements that are 4.70mm high and are 18.5 lignes all take a "Flume" staff #U1487 or Ronda Staff #3712, other staff makers/suppliers you might be able to cross reference.

Thanks. I really appreciate the help Bila.

John

No problem John, let us know how you go? Also just for future reference it is always best to post under dial and back plate pictures and actual physical dimensions when trying to ID a lot of the Swiss Calibre's, as it makes it a lot easier

My 2 cents. Unitas 343 movement.

Found this on EBAY for a Ronda 3712 Staff.

Update: I tried this staff and it wasn't the right one. It was too long, 4.65mm. I measured one out of a good watch and it measured 4.05mm. I ordered a staff from https://www.hamiltonparts.com/.
It comes in two versions, .8 and .9 collets. I think another possible staff would be a Ronda 2929 staff. The measurements match.

Thanks John for the update, looking at that movement and what bits it takes kind of smacks of a specific hybridized movement especially for Hamilton