Today we will take a quick look at the early anti-magnetic watches that were introduced by Orient in the late 1950s. But first, a little theoretical background.
Historically, there is a problem with watch mechanisms and magnets. When their ferrous components get magnetized, they no longer move about freely as intended, instead sticking to each other or themselves. In particular, this affects the balance spring, making it oscillate more quickly – which results in the watch running too fast.
There are generally two approaches to solving this problem – you may either use non-ferrous components, or shield the movement from magnetic fields.
Today, the preferred approach in most cases is the first. Materials like Nivorox (Nickel-Iron alloy) and similar were first put to use, improving magnetic resistance sufficiently so that most watches in recent decades could satisfy the anti-magnetic standard for watches, "ISO 764", namely to resist up to 4,800 A/m (60 Gauss). Lately, more manufacturers turned to using Silicon balance springs, achieving even better results.
Mind you, 60 Gauss might not seem like much when you think of watches such as Rolex Milgauss taking on 1,000 Gauss, but in fact a thousand Gauss is very much, way more than most of us would ever encounter in our daily lives, and 60 is just fine.
The other option, to shield the movement, is basically about placing it inside a "Faraday cage" – an inner casing made usually of soft iron, which is easily magnetized (and de-magnetized). It essentially attracts the magnetic field and prevents it from affecting the movement inside. This method is less common today as it makes for a heavier, more complex construction; and, it loses its effectiveness with any hole put through the cage, preventing such features as a date window and other "complications". However, before non-ferrous balance springs were available, this was the best way to achieve high magnetic resistance.
Orient Para Aimant
In 1958 Orient decided to launch an anti-magnetic watch of its own, which would be the first among the Japanese watchmakers. Naturally, the brand did not have the resources to delve into new material research, and chose the "cage" approach.
By then, Orient had already introduced the modern N-Type movement. However, it chose to build its antimagnetic model around the older T-Type caliber, which was considerably smaller (23.30 vs. 25.50mm). This way they could keep the size of the watch down, despite the added width of the cage.
In the following picture, you can see the main cage, next to the caseback. Not visible in the photo is the metal disc which lies beneath the dial, which closes the lid over the movement, with only two little holes left for connecting the crown and the hands.
Curiously, Orient chose to call this new model "Para Aimant". Now, Paramagnetic is the proper term for the soft iron cage – which by the way isn't really soft, it's just the term used to differentiate it from hard iron, which is harder to de-magnetize. And "aimant" is French for magnet. But, paramagnetic in French would be "paramagnétique"…
Anyway, the cage did its job well enough. The watch was said to withstand 200 Gauss, more than three times the requirement of ISO 764.
A number of Para Aimant versions were made, with movement variations numbering 17, 19, and 21 jewels. These were probably priced in the range of 5,500 – 6,500 JPY, making them more expensive than most T-Type models, and very close to the high-end Royal Orients.
Orient Royal Super-Antimagnetic
Besides its quirky semi-French nomenclature, there was another problem with the Para Aimant: Citizen watch company was using the "para" prefix for its own products. In 1956 Citizen released the "para shock", its first shock-resistant watch; and 1959 saw the introduction of the "para water", Citizen's first water-resistant model.
Apparently, Orient wanted to avoid the commercial conflict, and seeing that their antimagnetic watch was already in the Royal Orient price bracket, the brand took a logical step: the Para Aimant was set aside, and in its place came the Royal Super Antimagnetic.
This time around, Orient used the N-Type movement, specifically its 17 jewel variant (likely in order to keep the price down). Photos of the Royal Super Antimagnetic do not reveal a separate cage like the Para Aimant, and Orient did maintain the same diameter with the Royal Antimagnetic as other Royal models – possibly, the case was built with the iron cage already part of it, making the whole construction more compact.
Anyway, to keep things at least a little quirky yet, in best Orient tradition, the Royal Orient's caseback still read "Para Aimant".
Pictures that appear on this post were taken from various sale ads and the 1999 Orient Watch Catalog book.