Tetra 27

The NOMOS Tetra 27 401 is the original compact Tetra reference, with a 27.5mm square stainless steel case, white and gray silver-plated dial, tempered blue hands, and a closed stainless steel case back. As a long-running Tetra model, it has gone through several hand-wound movement iterations over time, including 1T, 1TS, and 1TSP executions before the current Alpha calibre. The case measures 27.5mm by 27.5mm, with a height of 6.1mm and a lug-to-lug length of 38.5mm. It has a sapphire crystal front and a closed stainless steel case back. The Tetra case is defined by its square shape, compact proportions, and stepped lugs. Water resistance is rated to 5 atm - an upgrade over the original 3 atm. The galvanized dial combines white and gray silver-plated surfaces, with the small seconds display at 6 o’clock set apart from the main dial area. The layout uses the Tetra’s square minute track and printed markers, while the tempered blue steel hands provide contrast against the pale dial. The display consists of central hours and minutes with subsidiary seconds. Power currently comes from the NOMOS Alpha, a manually wound in-house calibre measuring 10 ½ lignes in diameter and 2.6mm in height. It has 17 jewels and a power reserve of up to 43 hours. The movement history of this reference reflects the early development of NOMOS’ hand-wound calibre family. The watch is supplied on a black Horween Genuine Shell Cordovan strap with an 18mm lug width.