Why do you say it was probably never registered? Have you tried to inquire with regards to the serial number? It might be best to have an attorney call for you with the serial number to determine whether it is in the NFRTR. If it isn't in the NFRTR and you can't find any documentation of registration or military bring-back papers, you can 1. forfeit it to the BATFE, 2. donate it to a museum and get a tax deduction, or 3. cut the receiver per BATFE specs and sell the parts. See also my article: http://blog.princelaw.com/2007/9/25/grandpop-s-machine-gun-in-the-chest
