Adding the /ANALYZE qualifier to the BACKUP /LIST command causes BACKUP to provide a structural dump of the save set.

$ backup login.com login.bck/save
$ backup /list /analyze login.bck /save
Listing of save set(s)

Block header
  SIZE      = 256
  OPSYS     = 2048
  SUBSYS    = 1
  APPLIC    = 1
  NUMBER    = 1
  STRUCLEV  = 0101
  VOLNUM    = 1
  CRC       = 7362C94D
  BLOCKSIZE = 32256
  NOCRC     = False
  SSNAME    = \"LOGIN.BCK\"
  FID       = 0,0,0
  DID       = 0,0,0
  FILENAME  = \"\"
  ATTRIB    = 0000000000000000
  FILESIZE  = 0

Record header
  RSIZE         = 176 = %X\'00B0\'
  RTYPE         = SUMMARY (1)
  FLAGS         = %X\'00000000\'
  ADDRESS       = 0
  BLOCKFLAGS    = %X\'0000\'

    STRUCLEV = 0101
    SIZE =   9, TYPE = SSNAME
      \"LOGIN.BCK\"
    SIZE =  31, TYPE = COMMAND
      \"BACKUP LOGIN.COM LOGIN.BCK/SAVE\"
    SIZE =  12, TYPE = USERNAME
      \"WILLIAMS    \"
    SIZE =   4, TYPE = USERUIC
      [7,6]
    SIZE =   8, TYPE = DATE
       7-MAR-2007 22:54:00.04
    SIZE =   2, TYPE = OPSYS
      0800
    SIZE =   4, TYPE = SYSVER
      \"V8.3\"
    SIZE =   9, TYPE = NODENAME
      \"_CLASS2::\"
    SIZE =   4, TYPE = SIR
      80000000
    SIZE =  12, TYPE = DRIVEID
      \"_$22$DKA300:\"
    SIZE =   4, TYPE = BACKVER
      \"V8.3\"
    SIZE =   4, TYPE = BLOCKSIZE
      32256
    SIZE =   2, TYPE = XORSIZE
      10
    SIZE =   2, TYPE = BUFFERS
      1238

Record header
  RSIZE         = 256 = %X\'0100\'
  RTYPE         = FILE (3)
  FLAGS         = %X\'00000000\'
  ADDRESS       = 0
  BLOCKFLAGS    = %X\'0000\'

    STRUCLEV = 0101
    SIZE =  22, TYPE = FILENAME
      \"[WILLIAMS]LOGIN.COM;55\"
    SIZE =   2, TYPE = STRUCLEV
      0201
    SIZE =   6, TYPE = FID
      28639,3,1
    SIZE =   4, TYPE = FILESIZE
      35
    SIZE =   4, TYPE = UIC
      [7,6]
    SIZE =  32, TYPE = RECATTR
      0000000000000000000000000000000000000168000400000023000000590202
    SIZE =   6, TYPE = BACKLINK
      19429,3,0
    SIZE =   2, TYPE = FPRO
      System:RWED, Owner:RWED, Group:RE, World:
    SIZE =   2, TYPE = RPRO
      System:RWUD, Owner:RWUD, Group:RWUD, World:RWUD
    SIZE =   1, TYPE = ACLEVEL
      00
    SIZE =   4, TYPE = UCHAR
      00000300
    SIZE =   2, TYPE = VERLIMIT
      32767
    SIZE =   1, TYPE = JNL_FLAGS
      00
    SIZE =   1, TYPE = RU_ACTIVE
      00
    SIZE =   4, TYPE = HIGHWATER
      5
    SIZE =   2, TYPE = REVISION
      1
    SIZE =   8, TYPE = CREDATE
      23-JAN-2007 16:40:36.66
    SIZE =   8, TYPE = REVDATE
      23-JAN-2007 16:40:36.72
    SIZE =   8, TYPE = EXPDATE
      17-NOV-1858 00:00:00.00
    SIZE =   8, TYPE = BAKDATE
      17-NOV-1858 00:00:00.00
    SIZE =   4, TYPE = DIR_UIC
      [7,6]
    SIZE =   2, TYPE = DIR_FPRO
      System:RWE, Owner:RWE, Group:RE, World:E
    SIZE =   2, TYPE = DIR_VERLIM
      32767
    SIZE =  12, TYPE = ACLSEGMENT
      (IDENTIFIER=[5,12],ACCESS=NONE)


Record header
  RSIZE         = 2048 = %X\'0800\'
  RTYPE         = VBN (4)
  FLAGS         = %X\'00000000\'
  ADDRESS       = 1
  BLOCKFLAGS    = %X\'0000\'

Record header
  RSIZE         = 256 = %X\'0100\'
  RTYPE         = FILE (3)
  FLAGS         = %X\'00000000\'
  ADDRESS       = 0
  BLOCKFLAGS    = %X\'0000\'

    STRUCLEV = 0101
    SIZE =  22, TYPE = FILENAME
      \"[WILLIAMS]LOGIN.COM;54\"
    SIZE =   2, TYPE = STRUCLEV
      0201
    SIZE =   6, TYPE = FID
      20021,1,1
    SIZE =   4, TYPE = FILESIZE
      35
    SIZE =   4, TYPE = UIC
      [7,6]
    SIZE =  32, TYPE = RECATTR
      00000000000000000000000000000000000001E2000400000023000000590202
    SIZE =   6, TYPE = BACKLINK
      19429,3,0
    SIZE =   2, TYPE = FPRO
      System:RWED, Owner:RWED, Group:RE, World:
    SIZE =   2, TYPE = RPRO
      System:RWUD, Owner:RWUD, Group:RWUD, World:RWUD
    SIZE =   1, TYPE = ACLEVEL
      00
    SIZE =   4, TYPE = UCHAR
      00000300
    SIZE =   2, TYPE = VERLIMIT
      32767
    SIZE =   1, TYPE = JNL_FLAGS
      00
    SIZE =   1, TYPE = RU_ACTIVE
      00
    SIZE =   4, TYPE = HIGHWATER
      5
    SIZE =   2, TYPE = REVISION
      1
    SIZE =   8, TYPE = CREDATE
       2-OCT-2006 11:21:13.80
    SIZE =   8, TYPE = REVDATE
       2-OCT-2006 11:21:13.84
    SIZE =   8, TYPE = EXPDATE
      17-NOV-1858 00:00:00.00
    SIZE =   8, TYPE = BAKDATE
      17-NOV-2006 09:58:24.85
    SIZE =   4, TYPE = DIR_UIC
      [7,6]
    SIZE =   2, TYPE = DIR_FPRO
      System:RWE, Owner:RWE, Group:RE, World:E
    SIZE =   2, TYPE = DIR_VERLIM
      32767
    SIZE =  12, TYPE = ACLSEGMENT
      (IDENTIFIER=[5,12],ACCESS=NONE)


Record header
  RSIZE         = 2048 = %X\'0800\'
  RTYPE         = VBN (4)
  FLAGS         = %X\'00000000\'
  ADDRESS       = 1
  BLOCKFLAGS    = %X\'0000\'

Record header
  RSIZE         = 27120 = %X\'69F0\'
  RTYPE         = NULL (0)
  FLAGS         = %X\'00000000\'
  ADDRESS       = 0
  BLOCKFLAGS    = %X\'0000\'


End of save set