Declared Water Resistance

The term waterproof and its Italian translation «impermeabile» carried very different technical and commercial weight throughout the twentieth century than what contemporary language assigns to water resistant. This is not a matter of semantics: it is a history of patents, regulations, and marketing that anyone buying or selling vintage watches must understand.

The regulatory turning point arrives in 1970, when Seiko modifies cases and dials to comply with American legislation, which prohibits the use of waterproof as an absolute promise impossible to guarantee. From that moment water resistant becomes the international standard. Pre-1970 Seiko cases bearing the original marking are systematically more sought after by collectors, not from nostalgia but because that marking identifies a precise generation of production.

In British military circles, the acronym W.W.W. — sources attest to both Wrist Watch Waterproof and Watch Wristlet Waterproof, both circulating in period documents — appears engraved on the caseback of watches commissioned by the Ministry of Defence in 1945 as a replacement for the earlier A.T.P. These pieces, twelve references produced by as many Swiss manufacturers, are today collectively known as the Dirty Dozen. On the caseback the acronym is often accompanied by three impressions of the Broad Arrow, the Pheon, symbol of British Crown property.

From a construction standpoint, water-tightness is achieved through very different systems. The screw-down crown compresses a gasket against the case creating a positive mechanical seal: this is the solution adopted by diving watches. However, alternative approaches exist: Swiss patent 189190 by Schmitz Frères (1939) for the Gallet Multichron uses a clamshell case in which a bucket-shaped caseback slides inside the front portion and four screws hidden in the lug feet compress the two sections, with no visible screws on the caseback. The Bulova capsule-type casing system, Fachon patent from 1959, instead forms a unitary capsule of movement, dial, and crystal that inserts into an external bezel with integrated lugs: the crystal's grooves align with raised rings on the case, guaranteeing seal without external screws. More recent systems, such as the triple gaskets on the crown of the MING 22.01 GMT, achieve high protection without resorting to a screw-down crown.

At the bench I still learn something every time I open a case from the Fifties: the original gasket is almost always hardened or absent. A waterproof declaration on the dial and actual seal are two separate things. Before any immersion — even in tap water — a gasket service is the only concrete guarantee, regardless of what is written on the dial.