In these circumstances the amount of postage paid (shown on the box) qualifies the weight of the item (will bear too much for sending an empty box!).
@ thomasng
"but I don't know how to tell them it was a fake watch, and I obivously made a false declaration on customs. "
You dont say which origionating Postal Authority but the Customs Declaration generally has no bearing on the claim, insurance level and proof of value do.
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