Freezer Frame-Drain Heater (650, 550)
  650     Use Prior to Serial #1810000.
  550     Use Starting with #M/P1004775 & between
          #M964070-M964469 and #M984750-M985149.
          Prior to #M/P1004775 except between
          #M964070-M964469 and #M984750-M985149
          Part is NLA. If just the drain pan & pan
          heater are needed see 4201000