This Colt Model 1900 Long Slide was sold to the United States Government and shipped to the Springfield Armory in Massachusetts on January 11th, 1901 in a 50 gun shipment.
This Colt 1900 was part of the 2nd army contract of the model 1900. There would be a total of 300 Model 1900's that were shipped to the Army during it's short production window.
This particular Colt 1900 was shipped back to the factory at some point during it's life and was refinished and had the rear sight safety modified to have a fixed sight put in place.
The K on the right trigger guard was applied for pistols that were sent in for repair or refinishing. Normally there would be a "RAC" inspection stamp in this area.