Whatever is advanced we have to accept the conjectural aspect of the discussion. There is not, so far, a definitive answer to be had on this subject . That is why I offered an explanation rather than anything more certain. I've been collecting watches since 1979 and I have never seen this configuration, and while that may be a statement about my life experience I would suggest that if it ain't got a star it ain't a Constellation dial. It could be a 2648, who knows?, but that doesn't make it a Constellation.
The very first Constellation launch Ads showed the star, and comparing Geoff Chiang's 2648 serials we know that both pieces came out about the same time, with the example being discussed produced marginally later. Case serials on the Chiang examples are slightly later than the example under discussion, which would lead me to think that it may possibly be a 2648 but not a Constellation, but the spacer is still an unresolved issue and it worries me as that is, from memory, a first too. The case back has little depth as opposed to the deeper bowl-like case backs of other 2648s. In fact it looks a lot like a 2500 case back designed to house a 30.10 calibre.
I proposed that it may have been from a 14311 as I have seen that style of dial on 14311s before, or it could be from one of the many iterations of Chronometers that Omega was pumping out in the very early 1950s to meet demand for this type of watch, but I am far from Convinced that it is a Constellation.
Cheers
Desmond