The present Longines chronograph reference 21391 is, without a doubt, one of the rarest, most attractive and best preserved Longines chronographs to come to the market in recent years. It is not only in all original and unrestored condition and features also a number of very rare technical elements but also an interesting history. In fact, the Archives of Longines confirm that it was sold originally to China. The most unusual feature can be found on the dial where, underneath the Longines signature, it is printed “NO-MAG” (for non-magnetic). We cannot remember having seen another chronograph with such a designation on the dial. The case back is characterised by the unusual “two ears”, a feature to help watchmakers to more safely open the case back in view of its enhanced water resistance. The case has most likely never been polished and harmonises very well with the period flexible steel bracelet composed of outer polished and inner satin finished links.