Case: Stainless steel, with screw-down crown, and a display case back. Sapphire crystal. Water resistant to 200 meters. Integrated bracelet. Signed. 

Dial: Black with luminescent roman numerals and hands. Hours, minutes, subsidiary seconds, with chronograph functions, GMT hand, and date window at 3 o’clock. Tachymeter scale. Signed. 

Diameter: 41mm, thickness: 14.5mm.

Movement: Automatic, Valjoux 7750 GMT. 25 jewels. Signed. 28,800 semi-oscillations per hour. Shock-resistant and anti-magnetic.

Condition: Watch is in good condition, with nice aging of the tritium lume. Timekeeping within COSC. 

More about Sinn:

Sinn Spezialuhren GmbH is a German watch manufacture based in Frankfurt. Founded in 1961 by Helmut Sinn, a former pilot and flight instruction, Sinn has quickly developed a reputation for its precise and durable tool watches, and in the 1970s, the manufacture produced watches for the German Air Force.