Zenith Chronomaster XT El Primero Flyback — Steel 43 mm — Automatic flyback chronograph with exhibition case back — NOS with original set - 03.1250.4009/01.C495

Zenith Chronomaster XT, a men's flyback chronograph in stainless steel, 43 mm in diameter and 13.5 mm thick, with an in-house El Primero automatic movement visible through the transparent case back. Silver dial with guilloché finish and applied silver-tone Roman numerals, protected by sapphire crystal. Chronograph with flyback function, full calendar with day of the week, month and date, and tachymeter scale. Water resistance to 30 meters. NOS — New Old Stock — example, never sold and never worn, from our store inventory dating back to the years when our jewelry store was an official Zenith retailer, complete with original box and booklet. Black crocodile leather strap with a stainless steel deployment clasp. Reference 03.1250.4009/01.C495.

DESCRIPTION
The chronograph that changed the measurement of time
The El Primero is not like other movements. Introduced by Zenith in 1969, it was the first integrated automatic chronograph in history and, above all, the first to beat 36,000 vibrations per hour — a frequency that allows it to measure tenths of a second, when the standard of the time stopped at fifths. Fifty years later, it remains one of the very few production calibers capable of such precision, and this is why Zenith holds a place in haute horology that no other brand in its price range can claim.

The Chronomaster XT houses that caliber in a 43 mm case and showcases its operation through a transparent case back. It is a choice worth understanding: the decorated oscillating mass and the balance wheel, which vibrates at twice the speed of a standard movement, are visible to the naked eye, and the hum of the high-frequency balance wheel can be heard by bringing the watch close to the ear. The watch itself tells you what is inside.

On this reference, the caliber is not limited to the chronograph. Built upon the El Primero base are two mechanisms that rarely coexist in the same watch: the flyback function and the full calendar.

Flyback is the feature that sets this model apart from ordinary chronographs. On a traditional chronograph, timing two consecutive intervals requires three actions — stop, reset, start. With flyback, one is enough: pressing a single button resets the hands to zero and immediately restarts the measurement. It is a complication born in aviation, where a pilot changing course could not afford to lose seconds, and it requires a specially designed mechanism: no chronograph achieves it by chance.

The full calendar indicates the day of the week, month, and date, three pieces of information managed by a single wheel train that advances at midnight. It is the complication that gives the dial its density of information and which, together with the chronograph, makes this Chronomaster a two-complication watch with overlapping functions — a configuration that Zenith produced in limited quantities and which is no longer available today.

This example is NOS — New Old Stock: it is not a used watch, but a piece that was never sold and remained in our store inventory from the years when our jewelry store was an official Zenith retailer. It has never been worn by anyone.

The case
Stainless steel, round shape, 43 mm in diameter and 13.5 mm thick. Fixed bezel. Sapphire crystal. Transparent case back, revealing the El Primero movement and the decorated oscillating mass. Water resistance stated by the manufacturer up to 30 meters (3 bar): the watch can withstand accidental splashes and rain, but should not be submerged or worn in the shower.

The dial
Silver with guilloché finish, which catches the light and changes tone depending on the angle. Applied silver-tone Roman numerals. Chronograph sub-dials, day of the week, month, and date indicators. Tachymeter scale along the perimeter for calculating average speed in kilometers per hour.

The movement
In-house El Primero automatic movement, produced by Zenith in Le Locle. Frequency of 36,000 vibrations per hour, allowing the measurement of tenths of a second — a historic feature of the caliber. The transparent case back makes its operation visible.

Functions: hours, minutes, seconds, chronograph with flyback function, full calendar with day of the week, month, and date, tachymeter scale.

The strap
Black crocodile leather with a stainless steel deployment clasp. Never worn on the wrist.

Operating condition
NOS watch, never sold and never worn. Stored in the jewelry store in its original packaging. Automatic winding, chronograph, flyback function, and full calendar tested and in perfect working order.

Transparency note: the watch comes with its original Zenith box and warranty booklet. Our jewelry store is no longer an authorized Zenith retailer: the booklet was not stamped by an authorized dealer, and the brand's international warranty therefore cannot be activated through us. This is already reflected in the price. The watch is covered by our jewelry store's 24-month warranty on its operation.

TECHNICAL SPECIFICATIONS
Brand — Zenith
Collection — Chronomaster XT
Model — El Primero Flyback
Reference — 03.1250.4009/01.C495
Condition — NOS, never worn
Case material — Stainless steel
Case shape — Round
Case dimensions — 43 mm diameter, 13.5 mm thickness
Bezel — Fixed, steel
Case back — Transparent
Crystal — Sapphire
Dial — Silver, guilloché finish
Indices and hands — Applied silver-tone Roman numerals
Date display — Yes, with full calendar
Functions — Hours, minutes, seconds, chronograph with flyback function, day of the week, month, date, tachymeter scale
Movement — In-house El Primero automatic
Frequency — 36,000 vibrations per hour
Water resistance — 30 m / 3 ATM
Strap — Black crocodile leather
Clasp — Stainless steel deployment clasp
Origin — Switzerland, Le Locle
Gender — Men's
Original list price — €12,500.00

INCLUDED ACCESSORIES
Zenith Chronomaster XT El Primero Flyback 03.1250.4009/01.C495 watch
Original Zenith box
Original Zenith warranty booklet, unstamped

WARRANTY
The watch is sold with our jewelry store's 24-month warranty on its operation.