Regarding conversion of model 1892 bolt-sleeves to model 1896 configuration:

Frank Mallory in his book, "The Krag Rifle Story", 2nd edition, page 217, gives January, 1900, as the Ordnance Department approval date for converting Model 1892 bolt-sleeves to Model 1896 pattern.

Joe Poyer in his book, "The American Krag Rifle and Carbine", page 142, wrote the conversion of bolt-sleeves to 1896 pattern started in January, 1897, and were used on Model 1892 rifles converted to the Model 1896 pattern.

William Brophy in his book, "The Krag Rifle", page 33, describes the conversion steps and states: "This sleeve was used on Model 1892 Rifles that were converted to the Model of 1896.

When Wolfsburg's model 1896 rifle was new, bright, and shiny, early in 1898, I would bet it was wearing a regular model 1896 bolt-sleeve.

FWIW - There probably were not a lot of model 1892 bolt-sleeves for conversion, until the early rifles were called in to make "model 1896 updates".