This is a very rare 1939 Longines timepiece featuring the renowned Caliber 13zn movement, known as the "Mushroom" Ref. 4270 1st Water-Resistant Flyback Chronograph in black, in excellent condition. During an era when various watchmakers were developing waterproof chronographs, often referred to as "Mushroom" or "Umbrella" due to their push-button design and the stepped snap-back waterproof case protruding from the middle case, Longines introduced this early water-resistant chronograph with its in-house Caliber 13zn movement featuring a flyback function.
The watch boasts a black gilt dial with telemeter and snail tachymeter scales, making it a standout piece among the highly coveted Mushroom models. It comes with its archive documents.