Late 1960s Longines Diver Chronograph "Big Eye" with Flyback Function, Equipped with the Renowned Caliber 30CH, Stainless Steel, 40mm, Ref. 7981-1. This is a rare first-generation model. Among the Caliber 30CH models, it stands out as a sports type with a classical design, featuring a 40mm rotating bezel, screw-back waterproof case, and a distinctive tachymeter black dial known as the Big Eye.
The specifications differ between the early 7981-1 and the later 7981-2 models. This particular piece is an early model with Caliber 30CH, slim luminous hour and minute hands, leaf hands on the sub-dials, and "LONGINES/WATERPROOF" engraved on the case back, making it a valuable initial model. It comes with the original bracelet (fits up to a 20cm wrist). Longines' in-house caliber chronographs are renowned in watch history for their precision and craftsmanship and will continue to be highly regarded and passed down in the future.