The seller could easily state in the product's description that the
pictured S/N is not the exact one that is for auction.
Buying a TEK scope,I would want to know the S/N of the unit I am
considering,as some TEK instruments have S/N breaks where it really
matters.It also gives me an idea of the age of the instrument.
(date codes from internal parts are more precise,though.)



I won't argue against that, nor would I bid on that scope.


And how would a potential buyer find out if any Ebay item is stolen?
Where does one go to check this?
AFAIK,there's not national DB of stolen goods that civilians can access.

Just as easily as anyone seeing the serial number in the auction could find
out. Funny thing is, if he'd simply made the picture more blurry or used
Photoshop to obscure the serial number it would have been far harder to spot
but that tape is blatantly obvious.