1. On nearly all makes of quality wristwatches you will see 'Swiss Made' below the 6 o'clock, this is not always repeated by the dial restorer and so you can tell if the dial has been restored. This is important as 90% of a the value of any watch is in the dial.
2. Always check a picture of the movement. This can tell you all about the true condition of the watch. If the movement screws are knurled or mashed it means that the watch has had problems and has frequently been taken apart.
3. Use your discretion, if it looks wrong it probably is. Check the sellers credentials etc.
Hope this helps - and don't forget to sign the Guest Book!