Notes Storage Facility (NSF)
The NSF has the following file signature: hexadecimal: 1a 00 (which is often followed by: 00 04 00 00)
NSF defines a ODS (on-disk structure) version. One significant change seems to be format revision 22 and later.
The NSF basically contains Notes.
Notes can use various forms of encryption see: Notes from Support: Notes Encryption - Locks for a Digital World.