[mothered]

if you don't; how do you provide a valid serial number?

Have a look on eBay, pretend you're Interested In purchasing a scanner from a given seller and tell him/her that you wish to confirm the scanner Is not stolen by cross-checking It's serial number.

As such, you'll have the serial number. Give the seller peace of mind that you'll purchase the Item once It's confirmed. Of course, you have no Intention to buy It.