MARC21       007m'15  Deterioration stage
     Values: 
              a   None apparent
                  Nitrate
              b   Nitrate: suspicious odor
              c   Nitrate: pungent odor
              d   Nitrate: brownish, discoloration, fading, dusty
              e   Nitrate: sticky
              f   Nitrate: frothy, bubbles, blisters
              g   Nitrate: congealed
              h   Nitrate: powder
                  Non-nitrate
              k   Non-nitrate: detectable deterioration (diacetate odor)
              l   Non-nitrate: advanced deterioration
              m   Non-nitrate: disaster