Historical Perspectives What Exactly Is A Sigma Dial? (And Why Does It Matter?)

With vintage watches, small details matter a lot. In fact, they're basically everything. When it comes to assessing the originality of a dial, this goes double, since any re-dial or service dial will dramatically impact the overall value of a watch. This explains the multiple questions surrounding the weird, round little marks sometimes found surrounding the "Swiss" or "Swiss Made" on watch dials from the 1970s. Those little marks are actually the lower case Greek letter sigma, and the dials are aptly called "sigma dials." The issue, you see, is that most of the plentiful information you find out there about sigma dials is wrong, plain and simple. So I decided to dig deeper and figure out when those sigma dials truly appeared and why. The story turned out to be even more interesting than I had expected.

The first myth perpetuated about the sigma dial is that those little letters were compulsory markings that Switzerland suddenly imposed on watchmakers sometime in the early 1970s. This could not be further from the truth, since the sigmas were a distinction chosen by the watchmakers themselves. To be more specific, it was the few watchmakers who were members of the l’Association pour la Promotion Industrielle de l'Or (APRIOR), an industry trade association for those making gold watches, which explains why sigmal dials cannot be found across all brands. In 1973, the charge was led by the Federation of the Swiss Watch Industry with a clear mission: promote when gold parts were used on a watch to enhance the perceived intrinsic value of a traditional watch.

One must remember the exact context of what was going on in the Swiss watch industry at the time. Mechanical watches were about to become technically obsolete as quartz movements were on the rise, in a world facing a strong economic recession, no less. And what better way to underline the deeper value of the good old mechanical watches than by mentioning their intrinsically valuable components. The sum-of-the-parts logic here might sound twisted at first, but it becomes much less so when correlated to the skyrocketing price of gold, which almost quintupled between 1970 and 1974. The sigma symbols were proof that the hands and indexes on a watch were made of solid gold. "A watch signed with the sigma is a durable investment," emphasized the APRIOR in marketing campaigns.

In the end, the Sigma initiative sounds pretty logical, if not totally convincing. In any case, it is not as innovative as the APRIOR might have pretended at its inception, since it bears a strong resemblance with the "OM" convention employed by Omega going back to the mid-1950s (and that you can see on the full gold Speedmaster Apollo XI reference BA 145.022-69 launched at the same time the APRIOR was formed). Omega had indeed chosen OM – Or Massif, or "solid gold" in English – to mark its dials manufactured in gold. It does not pertain to the hands and indexes, but conceptually remains very close, although we probably never could find proof of the influence of the OM markings in the APRIOR reasoning.

But, while the APRIOR was officially formed in 1973 (its by-laws being drafted in 1972), the sigma symbol was already trademarked in August 1971. This explains the confusion found in many sources dating the first sigma dials to 1973. If we look at the watches themselves – usually the best source of evidence – we can prove that the 1973 start date is completely wrong. 

You can indeed find plenty of Rolex watches with serial numbers dating them to the year 1970 that already bear the sigma dial. This means that there are not only sigma dials from before 1973 and the founding of the APRIOR, but also sigma dials from before the trademarking of the mark itself. This might be down to the initiative of a single dial maker for a few months before the trademark was filed and the broader plan sketched out.

If we look again at that trademark, we see that the it was continuously renewed until 2003, and that the APRIOR officially disappeared in 2007. Yet, looking at Rolex, it seems that sigma dials went away toward the end of the 1970s, though later than the 1975 cutoff that is often suggested. The beauty here is that the sheer volume of vintage Rolex watches allows us to track the time period of the sigma dial fairly easily. But it does not sadly provide a comprehensive understanding of the sigma mystery. There were indeed many other brands which had joined the APRIOR (five to nine members total at any given time) and for which dial suppliers such as Stern and Singer also provided sigma dials. Of those, the most obvious other names are Patek Philippe, IWC, and Vacheron Constantin.

A quick glance suffices to realize that many of the most prestigious models from Patek Philippe, IWC and Vacheron Constantin in the 1970s bore the sigma symbol – the Nautilus and the Ellipse d’Or from Patek Phillippe, the Ingenieur from IWC, and the 222 from Vacheron Constantin 222 (the square model). Interestingly, as with the Rolex watches, not all of these had solid gold cases; in many instances, a stainless steel watch benefited from hands and indexes in full gold.

Looking at those brands also lets you dive deeper into the real timeline of the use of sigma dials, since both the Patek Philippe Nautilus and the Vacheron Constantin Overseas displayed sigma dials well into the 1990s. This crucial information allows us to dispel the last of the big sigma dial myths – those are not necessarily service dials, they are perfectly correct as long as the watch matches the timeline of use by the specific brand, for a given family. Ideally, I would love to give a clear cut-out date for the use of the sigma symbols but nothing so definite can be established, except that last sigma dials I could find was placed in a watch produced in 2000 (note here that dials are made in batches, so it does not mean the dial was produced in 2000, but probably earlier).

Despite this imprecise disappearance, I firmly believe that there's true value in understanding what the sigma is all about and where you should expect to see it (and where you shouldn't). For example, a 1960s watch with a Sigma dial is for sure an incorrect configuration. And it is one you see often, even in the reference books that I consulted to write this article.

Looking back at the sigma dials, we have to give credit to the the APRIOR initiative, but at the same time we need to be honest about the sigma dial's real story: it was never an across-the-board measure envisioned for the entire watchmaking industry, and it did not prevent the Quartz Crisis of the 1970s in any meaningful way.

The enduring issue relates to the foundational assumption that end clients would truly value knowing whether some small parts of their watch were made out of precious metal. To me, it feels like a flawed one, as this type of knowledge just doesn't carry the emotional weight that the APRIOR was hoping for (nor were most customers probably even aware of the sigmas' presence).  After all, one must hope that no one would ever buy a watch with the sole purpose of melting it down to sell for scrap value; even if so, the sheer weight of 12 indexes and three hands in gold would not be worth too much at all. 

This explains two things: Why the sigma dial did not leave much of an enduring mark on the industry and why focusing on the appeal of craftsmanship was eventually the right call for the Swiss industry in the long run. But, there's yet another, deeper lesson to be had here as well: The world of vintage watches is a complicated one, and with all the bad information out there and the multitude of stories for any given subject, it always pays to do a little extra research.