I'd bet sporting money on cut, in this case. Long barrels were very much in fashion at this point in time. Look for the lack of or poor fill between the barrels and/or between the ribs at the muzzle (there is usually a void bounded by the insides of the barrels and ribs). Is there a steel "keel" to fill the muzzle void? Look for OE bead and bead placement. Look for poor finish on the muzzle "faces;" saw tooth marks, file marks, scratches, out of square, etc.