There are hundreds of prototypes out there still waiting to surface and a good few do every year. Back in the day there simply wasn't the regulation around these and many were made as almost dealer samples so made their way out of the factory, for those that didn't they were simply taken home by the team. I bought 1/5 calibre 1500 Elephants directly from the project director for the Marine Chronometer (John Othenin-Girrard), he simply took it home when they had finished with them, there just wasn't any value in prototypes as effectively they were products that were deemed not good enough to go to production.
I own quite a few prototype Omegas, this one is an interesting one as non of those combinations have ever been seen before and I cannot find any reference to it recorded in journals. The source (as you no doubt know) is watchco and this is likely to be coming from the owner's private collection.
I think the price is very steep and would see this as a more £2000 - £4000 watch (especially without any extract or evidence, which is notoriously difficult to get for prototype............. unless of course you are Christies...........................) but it is a very interesting specimen and with the insanity around Speedmasters and the 11003 Radial prototype and Speedmaster 1040 prototype in Tissot Navigator case going through Christies 50 for such huge sums this does seem to be somewhat of a bargain in the current climate around anything Speedmaster related
This NASA issued 1045 Radial prototype I can clearly see the value in simply because of the provenance around the piece and even if there were no extract (which there isn't for a lot of the NASA issued watch but surprisingly was for the Christies examples) would still be worth a mint due to the star made prototype case and radial dial.
The challenge around the example for sale is that the case back is from a standard production 1045 Speedmaster Chronograph, the dial is without doubt a prototype and on the basis that the last 1045 Radial dial (dial only same as the one pictured above from the Christies sale) that watchco sold a couple of years back went for £4000 on its own this seems like a good benchmark.
The additional challenge and bigger concern around the eBay example is that there are dozens of brands who used the 1045 movement so although I think it is complete plausible the this could well be as it left the factory fundamentally the top case could be one used by another manufacturer. We have seen examples of this recently, the Christies 1045 pictured below realised $25,000
Whilst is came with an extract (god only knows how Christies managed to 'extract' that info) fundamentally the watch is a proto 1045 movement in a production Tissot Navigator chronograph case yet because it hold the badge of proto, the extract and the unique number on the main plate and the case is worth 10X what a normal 1045 is worth and 20X what a Tissot Navigator 1045 is worth
The eBay watch clearly has a prototype dial (rare and valuable in itself) and prototype movement (but fundamentally is is just a production movement with a prototype serial, I see nothing unique in the movement design that sets it apart, much like the prototype from Christies) but the case has no clear Omega lineage and the case back is from a production variant.
IMHO knowing the vendor very well it is a completely legitimate prototype and following on from the Christies auction is well within the realms of what the christies watches achieved but IMHO the hype around Christies over inflated the prices and caused a frenzy (lets remember the dog of a 2915-1 which went for £100K) so with that in mind I would say the bay watch is perhaps overpriced at the current full asking price, but who know maybe they will take an offer or maybe someone with very deep pockets who 'must have it' (one of the Hodinkee squad) will dip in to their coin purse and pay the full asking price