The hallmarks are inside the bezel, so quite hard to see, they appear to be British hallmarks, the 9 is visible clearly with a loupe and a torch, I think the photo shows it ok. The stone is not real emerald, and it has some wear if you look closely.
The size is 'O', see photo with ruler for internal diameter. The item weighs about 2.15 g. Overall a flashy ring, at a budget price.
Box not included, that is to aid photography only.