Jim from thefiringline.com had some interesting thoughts.
Jim said;
Under CURRENT regulations by BATFE, if you're a gunsmith and modify a gun severely enough, you've "manufactured a new gun while destroying the old one" and at that point, you (the gunsmith) have to attach a new serial number linking back to YOU, the manufacturer. And you'd better have the right Federal license to do all this.
The point at which the mods are "severe enough" to kick this into effect aren't very clear, but if made today your Nana's gun would absolutely qualify: caliber, barrel and cylinder are all swapped.
Today, a lot of gunsmiths have manufacturing licenses for that reason. Take a look at the custom revolvers of Gary Reeder for example, he has a manufacturing license and re-marks guns that started with a Ruger frame all the time:
REVOLVER LISTINGS INDEX PAGE
I know for a fact Reeder has a full manufacturer's permit same as S&W or Ruger. In fact, in addition to modifying Ruger and Freedom Arms revolvers he's done small runs of his own totally scratch-built guns from the frame up.
As an example of how this area of law works, if you call up Reeder and have him buy a Ruger Bisley Hunter in 44Mag and have it modded to, say, this:
http://www.reedercustomguns.com/revolvers/510gnr.htm
...you can. He finishes it, and it arrives at your dealer and gets sold to you as a "Reeder 510 Hunter" or whatever with a REEDER-SUPPLIED serial number - original Ruger markings and serial number are stripped off.
Same as what Nana's gunsmith did.
Most of those Reeders are modified to at least the same degree as your Nana's critter, which is now pretty well confirmed as having started life circa WW1 as a .45ACP.
So, despite the dire warnings by some on that thread that the gun is "contraband", I think the fact that you can prove it IS heavily modified (started life as a WW1 45!) saves you.
The gunsmith pulled the original serial number and added his own, same as Gary Reeder does today. Did the gunsmith hold a manufacturing license like Reeder? Who the hell knows, we have no clue who the dude was. Probably not, but nobody can prove either way whether or not he had the right Federal permit. We don't even know if it was modded in Alaska (good thing because it's quite possible there were NO licensed manufacturers in Alaska pre-1955!). But the result today is a gun that is modded to the same degree and in the same way as guns we know are 100% legal such as Reeder's.
Now, I wouldn't carry it as a CCW piece(!) but...I think you'll be OK. You're verging just a little into "gray area" here and a really nasty Federal prosecutor who's trying to jack you up for something else might try and make a case. But as long as you're not running a meth lab or bestest buddies with Osama Yo Mama I think you'll be OK
Thoughts?