The Federal Firearms Reference Guide is an invaluable reference, in this case p189:
When a corporation, partnership, or other type of business entity Special(Occupational) Taxpayer goes out of business, the business may continue to possess firearms other than machineguns registered to the business only if the corporation, partnership, or other type of business entity continues to exist under State law and only if title to the firearms remains in the business after the Special (Occupational) tax stamp expires. Prior to a corporation, partnership or other type of business entity ceasing to exist under State law, all NFA firearms registered to the entity must have been properly transferred to another person. Transfer applications must be submitted and approved before dissolution occurs to avoid placing the possessors in violation of the NFA. If the registered machineguns are transferred to officers or directors of a corporate registrant or individual partners of a partnership, the transaction is a transfer subject to all applicable provisions of the NFA and GCA, including payment of tax.
Any NFA firearms retained by the business that were imported under 26 U.S.C. 5844 for use as samples or for scientific or research purposes may only be transferred to government agencies for official use or to a Federal firearms licensee who has paid the special (occupational) tax to manufacture, import, or deal in NFA firearms.