Some tips:
1) Since most quoted prices include shipping, you're better off buying just one watch in every order in case it was lost/confiscated.
2) Ask the seller to ship in a post bag like those DHL Express Flyers, they're more difficult to temper.
3) Ask the seller to declare the shipment as a Sample/Merchandise (i.e. Sample Plastic/Metal parts, but not Sample Watch!) with a very low monetary value (i.e. $2)
3) When the post bag arrives squeeze it first to see if something solid is inside. If it's a box weigh it or shake it.