Actually, /dev is a mounted file system -- see what the mount command reports.

It is not a remote file system like NFS, but then Linux doesn't differentiate "remote" file systems from other kinds of file systems (like /proc or EXT2 or NTFS or FTPFS).

The value of the device field identifies the handler (file system driver) that the OS uses to implement the file system object. If you only interested in NFS files, you could find out what its device id is and just check for that particular value.