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Extremely rare steel 67mm LONGINES Ref. 7411-2, split second / rattrapante chronograph and observatory! certified chronometer pocket watch with constant force escapement, powered by legendary Longines Cal. 262. In fact in 1968 this particular piece SN: 12303645 was submitted to timing contests to Neuchâtel Observatory, where scored N=5.84 (very good result)!
Legendary highly ingenious calibre 262, definitely the last cutting edge of mechanical engineering before the age of electronic timekeeping. The movement was conceived to be the most precise split-second chronograph on the market and it succeeded. It was responsible for timekeeping at several Olympic Games in the mid 20th century and at other major sporting events, including the Tour de France. The cal. 262 is manually wound, high frequency movement that runs at 36,000 beats per hour. It’s a large, robust movement with a diameter of 24’’’, or just over 54mm, with 26 jewels and a special Nivarox hairspring, self-compensating Guillaume balance and swan-neck micrometric regulator index. More importantly, the cal. 262 also includes a remontoir, or constant force mechanism, in the escapement, to ensure stable timekeeping even with the chronograph engaged. The ‘constant force’ mechanism consists of a small spring mounted on the seconds wheel and wound by the main gear train. It is this secondary spring which is supplying power to the escape wheel. As it is kept in virtually constant tension by the frequent winding, the power delivers to the escape wheel and balance is thus much more ‘constant’ than the usual gear train system.
The apex of Longines horological technology, comes together with its original sport timer case, in a great condition, the dial is still with photo indicator on small seconds is in overall good 8/10 condition, running and ready to use!