The first thing that ought to be done is to request a factory letter. 1151XX is probably
a 1908 to 1910 gun - the guns close to this serial number are not well correlated with
their shipping date.
While its always possible, its highly unlikely that it was originally made as a smooth-bore.
It would have to have been a special order, which is why a factory letter is needed.
I own a 44 smoothbore, and I know a bit about having to get it through the BATF
process. Mine is from the 1950's, and because of its historical significance, BATF
classified it as a C&R. This is unique to 44 caliber; there is something in the regs
that exempts 38 caliber smoothbores. You would need to check this out.
If it really is a smoothbore, and not just a worn-out bore, then the cylinder chambers
should be bored completely through. Your friend can check that out. This is one way
of confirming what the gun actually is.
Sending a copy of the factory letter to BATF is only one small piece of the BATF
process. Depending on the current regulations, they may not even care about a letter.
One of the problems with a letter, from 1908 - 1910 era, is that the invoices may not
exist, and so it might not be possible to fully document the gun. But - you have to
go through that hoop first.
Mike Priwer