Chronometer question

François Pépin

Maybe I am still not clear enough. I wanted to say that the 30 SC T2 18J seems to me to be an upgraded 30 SC T2, with a jewel on both sides of the 2nd wheel. A regular 30 SC would have 17J (or 16J for the first issues), right?

But I do not understand why Omega only put 17J afterwards in the 280-284 series. Oddly, the sub second series (260-267) had 17J (except the 265, with 15J), with 2 jeweled holes for the 2nd wheel, but the 280 series has only 17J (16J plus one for the second pinion, movement side), with only one jeweled hole for the 2nd wheel (movement side). The only reason I can think of is the fact that, in the SC series, the 2nd wheel is "digged" to let the second pinion go through it. But is that a real reason?

By the way, other exceptions are possible, I am not an expert and am only talking of what I have seen on a regular basis.

Sorry to spoil your post with my poorly worded remarks!

heavenscloud

I have nothing to add to this thread, but I would like to pre-order the chronometer book 😀