[descartes]

I have a Red Sub very close to yours-- 2,36M serial number-- with a Mark IV dial.
I bought it from a very well known vintage dealer who opined that the dial was one which was used during the overlap period when both Mark IV dials, and the last of the earlier dials, were being cased at the same time. The VRF case numbers project, and anecdotal evidence like your post @bjmcfp, appear to support this because there are certainly examples of Mark IV dials in cases which are earlier than the 2,45M referred to in mark's article. Still, it is hard to know for sure because there are few examples during the overlap period and originality is hard to verify.

I know there have been mixed views posted in this forum on this topic, and it is certainly possible that dials could have been replaced early on with a Mark IV dial (before the Mark V and VI dials went into production). Imagine, for example, a Mark II or III dial turning tropical (not necessarily considered desirable at the time) and the owner having it replaced with a service dial (which at the time was Mark IV because that is the dial which was currently in production).

In the interest of scholarship, it would be very interesting to see who else has a Red Sub with a case number lower than 2.45 which has a Mark IV dial. We could develop a catalogue which could help put finer point on the 2.45M figure used by Mark (which he himself admitted was only an estimated range). Given the rising popularity of Red Subs, this may be of value to people on the hunt for a Red Sub to help consider originality of a watch.

Here's a photo of my Red Sub.