THE WATCH:

The Respirator was one of the rare square watches to be water resistant, relying on a similar construction found in the Heuer Monaco. This Luxe version offered for sale is powered by a high-beat (28,800/bph) cal. 2542 PC automatic movement, in perfect running condition.

The 2542 PC has 23 jewels, a 48 hour power reserve, and beats at 28,800/bph. It features a screwless Glucydur balance and fine regulator adjustment by eccentric screw. It winds on ball bearings via a click-wheel switcher on the crown wheel.

The Respirator was one of Zenith's iconic lines in the late1960s and early 1970s with its recognizable square shape. Connoisseurs will find a similarity with the Heuer Monaco as they share the same case construction, as both cases were manufactured by Ervin Piquerez SA. 

THE DATA:

Maker: Zenith
Model: Respirator 28800 Automatic
Year: 1960s
Material: Stainless steel
Dimentions (WxHxT): 30x40x11,5mm
Caliber: High-beat (28,800/bph) cal. 2542 PC, automatic
Bracelet/Strap: Leather Nato 
Lug width: 20mm