DS is 15 soon and, obviously, has asked for a pocket watch 
I know nothing about such things. I don't want to get a shite chrome plated one that will last 5 minutes but I also don't want to spend loads of money because he is liable to lose or break it (ASD/ADHD/dyspraxia). I think he'd prefer a fairly heavy one, second hand/vintage would be fine.
Where does one buy such things? We don't have much in the way of shops here so ideally online but buying vintage watches online seems like a recipe for being ripped off!