The Frame was designated as the location that the ser# of the firearm would be located.

In 2002, the BAtf set specs for the ser# impression.
It can be impressed (stamped), engraved, cast into place on the frame.
Letters/Numbers must be at least .003" deep and 1/16" tall.

(ATF orig want the min depth at .005", but so many of the Mfg'rs complained during the public comment period that they'd need to purchase new expensive equipment to comply and some firearms frames would be damaged by such force that they backed off the to .003 figure.)

You can apply for alternative methods of impression. The DotMatrx was one and that was approved. Laser etch probably also.

To the BATF, it's all about Gun Tracing.
That's one of the big things they are involved in.
They run it and are the only one like it.

So anything that extends the reach, gives them more data and control on how ser#s and other mfg markings are applied is right up their alley.
National Tracing Center | Bureau of Alcohol, Tobacco, Firearms and Explosives
It's a 'for L/E use only' operation.
One of the Trace Centers separate divisions is set up specifically for tracing guns with removed or obliterated ser#'s. There's even a Form for that!


I don't personally recall an FFL license granting the holder the right to move a ser# and restamp it in another location on a firearm.
I was a 01FFL since 1971 and just turned it back in.

One thing they did allow you to do was to move the ser#, BUT with the approval of the ATF first.
That approval would come (or not) but first you would request the action and 'why'.
No action by you the FFL till ATF says yes.

It was sometimes done when for instance placing the butt swivel on a S&W. It would go right through the factory ser#. That's a bad thing (obliteration of a mfg factory imprinted ser#).
Request a ser# move for the reason of installing a 'factory style swivel' was common.,,and you used to get a positive response.
Do the work, move the ser# over and remark it.
BATF had their record for the big file cabinet in DC,,you were safe from the law that said you weren't supposed to remove, obliterate the ser#. (A law which went into effect in 1938, The Federal Firearms Act).
You put that BATF OK'd form in with your paperwork.

As time went on, the regs didn't change over this, but ATF seemed to. It got to the point where any request to change ser# loc on a firearm for any reason were not approved. Didn't matter if it was for work like above, cosmetic like engraving, or restoration.
I even had a BATF Compliance check where the Agent told me to halt work on a SxS shotgun frame because I had gold inlaid the ser# on the frame.
His on the spot decision was that I had altered and obliterated the orig ser#.

I talked with him at length about the fact that it was commonly done and has been for a couple centuries or more and that the ser# was still the orig. ( I did not want him to confiscate the frame as I figured I'd never see it again even if the outcome was favorable to be)
Showed him pics in multiple books of the same from many engravers and time periods.
He finally decided not to confiscate the frame ( a customers 5 figure shotgun) but instructed me not work on it and to wait till I heard back from him on this.
A week later I got the go ahead to continue. I was not a felon.
Precious metal inlay or filling of factory markings was OK.
..and the customer still had his shotgun.
Finished up real nice too.

You never know how an individual L/E officer will see a missing or altered number on a firearm.
Some don't even know what they re looking at.
The extreme other end of the spectrum is one who sees the tip of a felony crime syndicate.

But the Fed & State regs are absolutely clear on the matter of what's legal and what's not when it comes to the factory imprinted ser#on a firearm.