I have only seen pics of 2 known gens (the 1st was posted on VRF a couple of years ago & the 2nd pic from the link above). So I think it is safe to say they are rarer than white 6542s, which is about as rare as a rare thing can get. Probably, in the same rarefied class as the
(Yachtmaster Cosmograph)
Waiter, cancel that order!
I just realized there is a pic of a red '42 in 1 of my (brilliant) Japanese Rolex bookazines, which, assuming it is gen (& I have no reason to think otherwise), makes it the 3rd red '42 I have so far come across (so, maybe it is not quite as rare as a Yachtmaster Cosmo ). In fact, this 1 also has a solid red GMT hand (they do exist & Rolex should have made them all this way because the standard small GMT is very difficult to see (probably why they went to the large hand in the later 1675)) & contains a depth rating printed (also in red) above the GMT Master text
Although I cannot verify this new watch's authenticity, I have yet to discover anything in this Japanese publication (which is a virtual treasure trove of Rolex minutiae) that rings untrue. In fact, I wish these things were written in English (sorry, Japanese only), because they are chock full of text, which, based on the pics, I am sure go into great detail & could probably answer alot of questions