It's a Vertex WWW issued to the Army about 1945/46
Hands have been relumed as some point, but it has the original dial. Not so sure on the second hand. Case back is correct.
It's one of the 'dirty dozen' but not one of the better quality ones. In decent condition they are £1000 (ish) retail but I am not sure I would pay that unless that was the one I was looking for. £700 seems more likely currently.
It's well worth spending a bit of money on it to get it running (dependant on how much you paid)
I love WWWs great vintage watches in a modern size.
Have a look over at the BWM section there is a thread showing a Vertex WWW in Austin Kate's window