The ref. 3418: the Amagnetic

Anti-magnetic watches were designed with scientists and engineers in mind

During the late 1950s, Patek Philippe developed and marketed its first anti-magnetic wristwatch references. These watches were made in response to increased demand for high quality Swiss watches that could be used by professionals who had constant exposure to high degrees of magnetism such as electrical engineers, scientists and doctors. In such professions, a normal, non-protected watch would be rendered useless.

With Patek’s Amagnetic watches, the most sensitive parts of the watch, the anchor and escape wheel, were made using non-magnetic metals such as gold. In addition, numerous alloys had been proven capable of withstanding magnetism, namely Invar (composed of iron, nickel, carbon and chronium), Glucydur (berylium and bronze), and Nivarox (iron, nickel, chronium, titanium, and beryllium). Since the late 1950s, most Patek Philippe watches have been fitted with Nivarox hairsprings to help prevent magnetism. The first anti-magnetic caliber utilized in a Patek Philippe wristwatch was the caliber 12’’’-400 AM (AM representing anti-magnetic). Launched in 1958, this caliber was fitted with a gold or beryllium lever escapement and had a protective soft iron cap. These watches were designed to withstand magnetic fields of up to 450 oersteds.


The Amagnetic or anti-magnetic ref. 3418 was launched in 1958 and was in production for four years. Made only in stainless steel, these ‘tool’ watches were made with a waterproof four-piece case construction with convertible modules, a patented design that allowed a strap model to be converted to a bracelet model without the use of lugs.

This unusual watch complemented Patek’s steel tool watch offerings of the era and was available for purchase concurrently alongside the ref. 3417. While over 500 examples of the ref. 3417 were made, fewer than 100 examples of the ref. 3418 were made and only 40 of these watches have surfaced to date.

The 35 mm cases of the ref. 3418 were made by Jean Vallon in Neuchatel and the bracelets by Cornu & Cie in La-Chaux-de-Fonds. A fun fact is that the buckles of their bracelets were typically signed ‘UNROC’, Cornu backwards. Available with the option of silvered or black dials, this classic reference is as understated as it is functional. The original price was not inexpensive for the time, at 1,000 USD suggested retail.

Visit the Collectability Shop to see the ref. 3418.

Patek Philippe Reference Facts

Reference Number: 3418
Metal Availiabilty: Stainless Steel
Guesstimate of Production Number: 200 or fewer
Nickname: The Convertible  
Size: 35 mm
Caliber: 12 AM 400 (first series) 27 AM (second series)
Years of Production: 1958–62

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