You might have some luck trying to find a match on
https://www.omegawatches.com/planet-omega/heritage/vintage/ though Omega seemingly churned out hundreds of different watches under the De Ville name - chronos, automatics, quartz, and in totally different case styles too.
As for the case back and the movement - it's certainly not integral, so must be stuck. I'd take it to a jeweller and ask them to pop it off.
The watch isn't likely to be very valuable - a few £100s maybe - so it's not like you'd be ruining a priceless timepiece if you had to jemmy the stuck case off.
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