I have owned several ref. 666 Ingenieurs, and seen many in person. That does not insure that all of my related opinions will necessarily be correct, of course, but I do have a fairly deep knowledge base.
While it is true that not all vintage IWC watches featured italicized "SCHAFFHAUSSEN, an extremely high percentage, at least, of ref. 666 Ingenieurs did.
The fonts on yours are also thicker than what was typical of the early Ingenieurs, and feature more pronounced serif style. There are other differences in the styles as well, notably the W in Watch. The finer version typically seen on the early 666 is clearly different. You can compare the two below.
As for the second example to which you linked, it is superficially supportive of possible originality. But I'm not convinced of its originality, either, in part because mine had the typical signature. It is possible that there were a very small number of anomalies, but given all of the evidence of hundreds of photos of ref. 666 dials, and the consistent style seen in period advertising material, I'm yet to be convinced.
Again, to be clear, there is a possibility that the dial is original.
There is another difference between this early dial variation and the vast majority of subsequent ref. 666 dials that is worth noting: the indices are embossed, rather than having been "applied". Embossing is a cheaper process, as applied indices are, with rare exceptions, more finely sculpted, more robust (either steel or gold), and make a higher-class impression to the eye.
The related dial surfaces are also finer in the later variations, including "sunburst" styles.
The example of your early reference that I owned was in excellent condition for its age, but I ended up selling it and replacing it with a later dial variation in part because the dials with applied indices are more finely finished. If you have the opportunity to handle a later version in person, you should take advantage of it, and compare the two types of indices and dial surfaces.
I'm not sure I understand this. The watch seems to have normal aging for 70 years, including radium burn. And why would you want to find a new dial if you believe it to be original?
There was never any doubt that the dial variation existed, in fact I mentioned in my first post that I owned one.
The questions revolved around whether or not the dial was original, refinished, or a service replacement, and an advertisement does not shed any light on the answer to those questions.
