Folks if the smooth bore barrel is under 18 inches it is NFA regardless of any letter.
A letter is only for the addressee. AND the best thing to remember the ATF screws up an awful lot but they will still prosecute you for their mistake.
IT IS NFA with all needs for the legal possession.
Fees=
Form 1 for SBS, SBR, Suppressor, AOW =$200
Form 4 for SBS,SBR, Suppressor,=$200
Form 4 for AOW =$5.00
Don't get caught without an approved paid for one.