Code:
09/09/2003 06:34 2,149,759 spells_en.txt
30/03/2004 02:48 2,778,390 spells_us.txt
Spells_en.txt has not been updated since September 2003, while Spells_us.txt was updated at the end of March 2004, so it would appear that SOE has stopped using spells_en.txt and are now only updating spells_us.txt (for the English versions at least).