These are 720k disk images.  You need Teledisk to recreate the disks.
Teledisk can be found at:

    ftp://tvdog.shacknet.nu/tandy1000/system/teled212.zip

The disks should be labelled:

Msdos.td0         MS-DOS - Startup & Operating
Utilitys.td0      Utilities 02.01.01

These are the original disks for the 3000NL, BIOS ROM version 01.04.02
or above.  Per Tandy Faxback, the SETUP.COM program on the DOS disk
must NOT be used on the 3000NL.  Instead, boot with the Utilities disk 
to enter setup.
