Rohan, your gun is definitely the model 700, made in 1950. The model 500 is very seldom seen, few were made. It utilized the Webley screw grip third fastener and the back of the action was scalloped. It also has the medium grade of engraving, which was rather elaborate and had much fancier wood with fine checkering. And they were made before the war. I own the only one I have ever seen. It is often confused with the Model 400, which was basically the same but with a straight back action. Your gun is very good and will last several lifetimes given proper care.

When an old man dies a library burns to the ground. (Old African proverb)