What law is violated if someone ADDS a number?
The current owner obliterated nothing.
If it were mine, I would examine the entire gun inside and out for a serial number. If none was found, I would stamp it with a number I made up and not think about it any more.
If you sell it someday thru a dealer, they will simply record the number they see on the gun without question and it then becomes listed in the system along with millions of others. It is not your responsibility to know he history of the gun before it came into your possession. If it came to you as a private sale there would not have been a 4473 filled out on it when you got it.
IF you ADD a number in place of the mfg'rs applied ser, and imply that the # you added is now the actual ser# of the firearm,,that is Alteration of the Mfg'rs Applied Ser#.
As far as FFL Dealers "will simply record the number they see on the gun WITHOUT QUESTION and it then becomes listed in the system along with millions of others."
What you describe is the type of dealer that might run a Pawn Shop that takes in known stolen items and looks the other way because he can make some money on them.
Who's gonna' know..
There's plenty of people around like that in many businesses, not the best of people and they certainly know better.
FFL's are given the info about funny looking ser#'s even before the FFL lic is issued.
Both in reams of print matr'l and in person by interview with BATF.
Looking the other way is a bogus excuse for not recognizing the obvious in most cases and then playing Mr Dumb to rationalize it all away.
Every FFL Dealer gets ATF Compliance checks. They can be long and tedious. During those the subject of altered and obliterated ser#'s is always covered again and again.
It's not like you've never heard of the subject and know nothing of it.
The ATF Letter posted is short and sweet.
It's the same language since 1938 when the law was past (FFA 1938)
Most States have copycat laws as well. Some even more strict covering additional factory markings along with the factory marked ser#.
Is the BATF JumpOut Squard ready to pounce on anyone with such a firearm?
No
Does the law and language exist. Of course it does. Try and argue against it's existance and how it doesn't pertain to you.
I see a LE Badge in the top line of your posts.
Shouldn't you know some of this stuff?