Well, It is hard to define what is true and what is not
By: Mark in Paris : May 9th, 2015-14:10
if we're talking about a way to say what is true to Patek's chronographs history. The 13-130 which was used for a very long time until the CH 27-70 was a 2.5 Hz too. But, apart from that detail, the 5170 layout (case, lugs, dial, hands, markings, Breguet ...