Looks like a Dennison cased UK model. Poss model 13322. Those were made from the early 1940s to the end of the 1950s. Yours looks to be a later rather than earlier one. The movement serial and hallmark letter would tell you more.
Nice heirloom
If you’re planning on wearing it Good idea to have it serviced by independent watchmaker with Omega parts account.
Members here can recommend one in your area
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