This article of Fratellowatches is quite instructive about the way the production date is determined: Either the day of assembly or, in case they have insufficient information, the day of shipment. But the day Omega got paid from their dealers for a specific watch? Why would they even keep track of that?
How can the archive know that the dial will age into soleil? Clearly added afterwards and quite disappointing to have extract of archive morph into a certification process.
The blue soleil isn’t result of aging those dials were produced blue soleil, they have never been black. Just to avoid confusion on that