Lampholder, SVCE (680, 690, 501R, 501F, 511, 532,
          542, 550, 561)
  680      Use Prior to Serial #2054736.
           Starting With #2054736 See 7022117.
  690      Use Prior to Serial #2054736.
           Starting With #2054736 See 7022117.
500 Series (EXCEPT 561) Use Regardless of Serial
           Number.
  561      Use Prior to Serial #1810000.
           From #1810000 to #2054736 See 3050190.
           Starting With #2054736 See 7012420