JustinG said

Putting a fake serial number on the antique device, which is not regulated as a fire arm (antique), for the sole purpose to defraud someone with the purpose to induce a buyer is called fraud by inducement. 

A misrepresentation for the purpose to deceive is illegal. A merchant or someone who regularly deals in “said items” who knows or has reason to know of a false material fact, and relies on this false material fact is also guilty of fraud. Someone can’t “hide” behind stupidity and claim it was like that. 

A merchant  in this particular situation has specialized knowledge he can’t escape by saying “it looks old”. He’s reportedly selling it as authentic, and has a duty to verify. 

Problem is, he’s relying on an unknowledgeable buyer who won’t second guess the items. He knows serious collectors won’t give it a second look.  

It’s a shame. 

This is NOT legal advice, it’s just my view on a hypothetical situation with limited information, and more facts are needed to make a reasoned professional judgment.   

You know Justin that there is only 1 Lawyer joke, the rest are true.