This is a 1960s Heuer "Type-1550SG" model made for the West German Air Force, equipped with a Valjoux 230 movement featuring a flyback function. It is a waterproof stainless steel chronograph with a 43mm case.
Powered by the Valjoux Cal. 230, which includes a flyback function, this professional chronograph was manufactured to military specifications. It features a highly water-resistant clamshell case with a rotating bezel, and a black dial with luminous Arabic numerals for excellent legibility.
With prominent crown and chronograph pushers for ease of operation, the 43mm jumbo size offers a bold presence while maintaining a well-balanced and solid feel overall—truly a remarkable piece.