How to tell whether your late 1930s or early 1940s ladies omega is a real mccoy

How to tell the real mccoy of Omega? Some of the indications must be there. Take the example below.

The typical Omega hallmark on the Dial, on the crown, on the movement and also on the inside of the case. The 1940s bootlace strap itself is not original, if yes, the clasps will have the Omega hallmark. Nevertheless, it will be hard to get hold of Vintage straps. So the overall, it is a nice piece of Omega. This piece fetched around US$1000.