What is the reference number inside the case back? I'm Pretty sure that is an ETA movement, (I don't know if Omega used these or not) but cant quite make it out.
As your movement does not any Omega markings (i.e.: Omega caliber 1438), it may be that the movement was damaged and replaced with a new movement, in this case an ETA 255.461, which is exactly the same movement Omega used, just with their markings.
I'm only pointing this out in case it comes up in the future and somebody tells you that it's fake because the movement isn't marked Omega.
As others have noted, it's not a fake and it's a nice watch. Enjoy it.