From "The Krag Rifle Story" by Mallory  pg. 68 "Because of the press of work in completing the initial issue of magazine carbines, conversion of Model 1892 rifles on hand to Model 1896 configuration did not start until March, 1897" These were then issued "interchangeably with the Model 1896"
Then on page 69 "no attempt was made to convert the early rifles already issued until the beginning of calender year 1900"
This is the best I can come up with!