[mothered]

for example, I tell that the watch is not in his box and they ask if I noticed any sign of tampering on the external box

If they ask for signs of tampering, say that you're not sure but will check and get back to them.

Take your time to reply - the claim my well be approved In the meanwhile. If It Isn't, that's when you mention the tampering. It serves as a backup If the claim Is declined.