HEUER. A MEN'S STAINLESS STEEL AUTOMATIC PILOT'S FLYBACK VINTAGE CHRONOGRAPH WRISTWATCH Model: Bundeswehr 1550 SG ‘3H’ Date: Circa late 1960's, early 1970's Movement: Signed 'Leonidas', 17-Jewels, Cal. Valjoux 230 Dial: Signed, black, green luminous Arabic numeral hour markers, white outer minute division, white sword hands with green luminous insert, white centre seconds hand with luminous insert, subsidiary seconds dial at the 9 o'clock position, subsidiary 30 minute dial at the 3 o'clock position, red '3 H' symbol at the 6 o'clock position Case: Signed 'BUNDESWEHR', brushed and polished stainless steel, black bi-directional bezel with silvered Arabic numerals, stainless steel crown and chronograph pushers, back secured with 4 screws, No. 6645-12-146-3774/6645-12-340-9456 Strap: Generic black leather with stainless steel buckle Size: 43mm The watch was originally produced for pilots in the German military, the Bundeswehr, with a rugged functionality designed particularly for navigators. The chronograph flyback function allows the operator to zero the chronograph with the push of one button while still being able to record the minutes on the secondary dial, especially beneficial for navigators. The red '3H' at the 6 o'clock position on the dial signifies the fact that this model has luminous paint with tritium, a radioactive isotope of hydrogen-3 hence the 3H, while the Valjoux 230 movement with a 48-hour power reserve further enhances the capability and usefulness of the watch in all situations. It is an icon of a vintage military watch and wears incredibly well. *The same watch can be found in the publication Military Timepieces by Konrad Knirim, pp. 574-575. (43mm.)