Thank you for your reply.
https://wahawatches.com/how-to-identify-a-vintage-omega-2019/
Here's what else I managed to find about the discrepancy between the serial numbers on the movement of the watch and the case of the watch
The calibre doesn’t match the case
The first and most obvious reason for that is that the watch is a “franken,” which means that it has been assembled from random parts
However, there’s one exception.
Always check if the movement in the watch isn’t a US version of the movement mentioned in the OVD. These will have a US import code (OXG) on the balance cock, and a lower jewel count. The OVD often doesn’t list the US version of a particular reference.
This is true for almost all families of Omega rotor automatics: 4XX, 50X, 55X, 56X, 59X, 71X, and 1XXX series. For example, the jewel count is the only difference between the 470 and 471, 490 and 491, 550, and 552. And so on.
You can find the details of the differences in the
Ranfft archive. Every entry for movements within a particular family list the differences between the movements within that family.
Otherwise, as mentioned in the previous part of the series, a movement that doesn’t match the case is a red flag.