You could dust it for finger prints.
Chances are that ASUS Q/A has tested the laptop for functionality prior to shipment (and prior to placing the seal). Did you buy the laptop from ASUS directly or through a reseller?
You could check the dates of various files/logs on your hard drive.
Make sure that windows is uninitialized (needed that first user/fresh install customization) but this is not foolproof, as perhaps Asus handles that for you.
If you are truly concerned, contact whoever you got the laptop from and file a complaint, demand a refund, or replacement.