Thank you very much for sharing those great photos of the dial, and for sharing the serial number of the movement. The dial appears to be convex. Apart from the curvature, I believe that there are some subtle but important differences between your dial and the "correct" ones that you posted. Before addressing the differences, I will say that I am skeptical about the two examples (first two photos are of the same watch) below. These dials are certainly similar to yours, but I think that they could have come from sei tacches.





Moving onto the "more likely to be correct" ones, the key difference is the sub-dial design, IMO. The first two examples (first two photos are of the same watch), have an "old" style of font that is prevalent on tre tacche dials. The next dial looks like those found in "DH" Longines from the early 1940s. [As a side note, I have also seen "DH" examples with the first dial below so it would be prudent to inquire with Longines before buying.] This sub-dial design is also prevalent on tre tacche dials. The last dial below is difficult to see, but the sub-dial appears to have a "railroad track" scale. In general, this type of scale is more indicative of a tre tacche dial than a sei tacche dial.

 

As a side note, fitting a convex dial on a flat dial «movement» will also
require changing of the hour wheel and cannon pinion to a longer type.
I have been chasing down that rabbit hole before

 

Good information, thank you. I suppose that a complete donor would have those parts.

 

Can you please share some phots of yours? I have a really hard time seeing the difference between the dials you call flat and the ones you call convex, even out of the case.

 

Again, thank you for sharing your knowledge.

Do you have any pictures of correct tre tacche dials out of their cases or know where I can find good photos to study them, because I still can't see the difference between flat and convex dials on these examples I shared.

Good point about the sub-dial design, as you say most correct tre tacches seem to have the older railroad style track. There still are many tre tacches with "my" sub-dial design on the web (from dealers, collectors etc) but you think they are all put togheter rather than untouched if I understand correctly?

Just saw @maanu latest 35mm tre tacche on IG which looks to have the same dial as mine (at least same sub-dial design), maybe you can share some pictures of the dial or information about your watch?
https://www.instagram.com/p/CX64COcPAMK/

 

Below are two examples of tre tacche dials out of their cases. To me, both appear flat, but I admit that it is difficult to discern.

Photos from: https://watchcharts.com/listing/264...e-12-68z-32-5mm-tretacche-sector-calatrava-3t



Photos from: https://omegaforums.net/threads/longines-21441-tre-tacche.65030/


Yes, it is my contention that the tre tacches one sees with "your" sub-dial are likely the products of dial swapping. I am happy to be proven wrong.

Below are two 35 mm tre tacches (ref. 3864) with the same order number (21'764). The first one (case number 159) has a dial that is in the correct style, IMO. The second one (case number 163) has dial that is commonly found in sei tacches. It is difficult to see the flatness/curvature of each dial, but I thought I would post them anyway.

Photo from: https://www.horare.com/products/1940s-longines-tre-tacche-35mm-black


Photo from: https://www.bloomberg.com/news/arti...-find-longines-gilt-dial-tre-tacche-calatrava

 

Would have love to see photos of a black dial out of its case since they are much harder to see the difference on flat/convex IMO. But I can see the flatness on those white dials but still don't see the difference on the two black dialed examples you showed (except for the clear difference in sub-dial design).

The last one with the wrong dial was for sale for 6200EUR, yikes.. And that was in 2015!

So to conclude most 35mm tre tacches you find now are not original and often have swapped dials taken from other models, that at least is an eye opener for me. I'm just glad I did not spend 6000EUR+ for mine!

 

Below is a comparison of your black sei tacche dial (convex) and a black dial from a ref. 5707 (flat). I have added a red arrow to each image to indicate the estimated direction of the light source. On your dial, this is evident from the difference in tone between the outer edge and inside the minute track. On the 5707 dial, this is evident by the small shadow opposite the red arrow. In contrast to your dial, the tone of the outer edge looks essentially the same as the tone inside the minute track.



Photo from: https://www.ebay.com/itm/194458579334?hash=item2d46a27186:g:5DoAAOSwPRJhcwET&nma=true&si=%2BQP%2F7deIqwSiAlQ7xmFxpeShBpQ%3D&orig_cvip=true&nordt=true&rt=nc&_trksid=p2047675.l2557Purchases made through these links may earn this site a commission from the eBay Partner Network

 

Yes its easy to see the difference in this comparison. But I find it way harder to see the difference on a glossy black dial like mine rather than this matte black dial and especially when they are in a case and the crystal makes its delusions.

Again, thank you for all your help. I will have my eyes open for a correct flat donor dial but with pretty small hopes and in the meantime wear this with joy, and since I found out many of the 35mm tre tacches already is not what they seem this makes me less anxious to actually find a correct dial!

 

Sam, your watch, be it with incorrect dial, is stunning
I would wear that little bugger with lots of pride.

 

Just for posterity, below is a glossy black dial from a very nice 12.68Z with center seconds. The serial number is 5'613'076 and it sold for $760 USD on Dec. 21, 2021. I believe that the dial is flat.

Photos from: https://www.ebay.com/itm/3137897391...=true&nordt=true&rt=nc&_trksid=p2047675.l2557Purchases made through these links may earn this site a commission from the eBay Partner Network

 

Another glossy black dial. This one is from a sei tacche and appears to be flat. While I am skeptical of convex tre tacche dials, there are are certainly flat sei tacche dials that are original.

 

Fantastic, where did you find this?
This would be exactly what I’m looking for I’m guessing!

 

This watch was for sale on eBay in 2020, I believe. I was very tempted to buy it and sort of regret not doing so. Oddly, I seemed to have only saved this photo. I cannot remember if it was a 12.68N or 10.68N. Maybe the latter.
I wonder whether your watch originally had a black dial. I would guess that it probably did not, given the blue hands. But I agree that a flat dial from a sei tacche could be a good candidate, though likely expensive.

 

A 10.68Z

 

Thanks for posting this. Based on the sub-dial design, this is one of those dials that I associate with sei tacches and not tre tacches. Below is a similar dial from a sei tacche. Possibly of note are the different 3, 5, and 7 hour markers. It is difficult to tell whether the dial is flat or convex. It looks convex but this could be the crystal. It would be very interesting to contact Longines and ask if there is any mention of the dial in the archive.

Photo from: https://www.tradera.com/item/190117...i-tacche-32mm-utan-krona-cal-10-68z-fran-1945

 

It's a 30mm tre.

 

Would be interested to know what @DirtyDozen12 think about the dial on this 35mm tre tacche posted in another Longines thread, is it flat or convex? Sub dial design is the one you recognize with sei tacches and not tre tacches.


In its case it pretty much looks like my dial

 

From this photo, I cannot tell whether the dial is flat or convex. As a side note, seeing the outer edge of the dial between 10 and 11 makes me wonder if the dial is convex. If the dial was flat, I imagine that the edge might be slightly more hidden. As you mentioned, the sub-dial suggests to me that the dial could be from a sei tacche. If I had to guess, I would say that the dial has been transplanted. But at this point, contacting the archive to see if there is any mention of the original dial (e.g. radium or not, silver or black, two-tone or not) would be my inclination.

 

Thinking more, I do not think that this makes sense.