PW Project Watch

Not everyone knows that, in the past, Zenith produced some diver watches with an immediately recognisable design.

Finding one of the Zenith diver models is not always easy as not many pieces have been produced.

Among the Zenith diver watches, there are the Defy Plongeur Ref. A3648, the Sub Sea Ref. A3630 and the Diver Ref. A3637.

Zenith Defy Plongeur Ref. A3648

Introduced in 1969, the Defy line was synonymous with reliability. It is no coincidence that it was called by Zenith “the safe of time”. The robustness of the patented case and impact resistance made it perfect for diving.

With an octagonal case of 37 mm the A3648 was distinguished by a beautiful black/orange dial. This contrast of colours was accentuated by the orange hands and the always orange rotating bezel in bakelite. The screw crown with double gasket placed at 4 o’clock provided better impact protection. This crown and a particular 3mm tempered (anti-scratch) mineral glass locking nut guaranteed the waterproofness up to 600 metres.

Initially the calibre was the 2552PC later it was upgraded and became the 2562PC. Both automatic movements had different hourly alternations. The 2562PC calibre had a frequency of 28,800 vibrations/hour, while the 2552PC vibrated at 21,600 vibrations/hour.

The movement was surrounded by a shock absorber ring whose elasticity ensures very effective protection against shocks. This elastic suspension system of the calibre ensured greater accuracy than the watches of the time.

As for the bracelet, the Zenith Defy Plongeur could be embellished either by the iconic Gay Frères skeleton bracelet or the rail bracelet from the same manufacturer.

Zenith Sub Sea Ref. A3630

Zenith Sub Sea ref. A3630 was first released in the late 60s. The watch featured a 39 mm stainless steel case that was water resistant up to 120 metres.

The black dial design with arrow hands and applied indexes was functional and easy to read. The date window was positioned, as for all Zenith watches, between 4 and 5. The black bakelite bezel, rotatable in both directions, contained the indispensable underwater scale for use in water. The screw crown was located at 3 o’clock.

Zenith used a total of three different movements for this watch. The first models came out with the 2542PC automatic calibre. Later, in the early 70s, it was upgraded with the 2552PC calibre. The 2552PC movement operated at 21,600 vph, has 23 jewels and provided a 46-hour power reserve. Finally, the latest versions were equipped with the calibre 2562PC. The 2562PC movement with 23 jewellery and a 48-hour power reserve, vibrated at 28,800 vph.

The famous Gay Frères bracelet with signed closure made the A3630 even more iconic.

Zenith Diver Ref. A3637

The Zenith Diver Ref. A3637 from the late 60s is a very rare vintage diving watch. Water resistant to a depth of up to 1000 metres, the A3637 was a reliable tool for a professional diver. The impermeability that this watch could guarantee was an important achievement for the time.

The A3637 was available in 4 colour variants: black, blue, yellow and black-orange. This choice is not accidental. In depth the visibility of colours is different. The orange disappears at a depth of 15 metres, the yellow at 25 metres and the blue that is the most performing is visible up to 50 metres.

Thanks to the clean dial, arrow hands and applied indexes, this model knew how to stand out from the others. Plus, the bezel matched with the colour of the dial made it a perfect diver to be used in depth. Obviously he could not miss the date window between 4 and 5 hours. The tempered (scratch-resistant) mineral glass was anchored via a data to the 43 mm case. This system together with the screw crown ensured the impermeability declared by Zenith.

When it came out on the market, this diver was animated by the self-winding 2542PC calibre. Subsequently, as with many other Zenith models, it was replaced with the 2552PC movement.

This watch was embellished with a Gay Frères bracelet with rails and initialled clasp.

Having passed more than 50 years it is difficult to attest to the coevity of these divers. It could happen that when a revision was carried out some parts were replaced or changed with what was available.

Born to be sporty and in step with the times, Zenith diver watches were and are full of character. Surely the maison of Le Locle will also amaze us in this field.