That's the issue..The Manufacturers Frame appied ser# is gone.
The has Manufacturers applied Ser# to the Firearm (Frame) been 'Removed, Altered, or Obliterated.....'
Just like it reads in the GCA, it's a felony to own, sell, recv, transfer, etc, etc.
Plus at this point, no one really knows if S&W Revolver cal 45 ser# 0251 is in NCIC GunFile as a Stolen Firearm.
That will be the first place any L/E agency will start.
The File searches and 'hit's by Ser# only, so there may be other hits returning. The added & misc info on each entry is used to separate and ID.
If clear (No Hit), the gun may just be confiscated anyway under the above Removed Ser# issue.
It may be given a pardon and with Heavens permission, the orig # restuck.
Sometimes the BATF will assign an 'ATF'prefix new ser# and that will be struck somewhere on the frame inspite of the fact that the orig# was identified.
I've had two such instances of this latter ATF ser# being stamped on handguns that had their factory ser# removed, Identified by lab process, the gun then restamped with the AFT# and gun returned to it's orig owner.
Lot's of things in motion...
A lot depends on who's on the other end when you contact someone.