Lampholder, Double SVCE (561, 600/600-2 Series,
          700-2/700-3 Series Tall Units)
  561     Use Starting With Serial #2054736.
          From #1810000 to #2054736 See 7016470.
          Prior to Serial #1810000 See 7015754.
600/600-2 Use Starting With Serial #2054736.
          Prior to Serial #2054736 See 7016470.
 700-2/3  Use From Serial #2054736 To #3151471.
          Starting With #3151471 See 7012420
          Prior to Serial #2054736 See 7016470.