The U.S. Krag was made only by Springfield Armory and only for the U.S. services. Some may have been sold overseas, after they became surplus, but there were no foreign contracts or metric sights. The Krag-Jorgensen system was used by Denmark (1889) and Norway (1894), but they differ from the rifle adopted by the U.S.
In that period, the sights were given model numbers separate from the model of the rifle or carbine they were put on. The Model 1901 sight was the predecessor of the Model 1905 sight for the Model 1903, which originally had the Model 1903 sight, very much like the Model 1902.
IMHO, the Model 1901 sight is a poor one, but the Model 1905 sight has to be the worst sight ever put on a combat rifle. In that day, Army Ordnance was run by the target shooters, and they (like their descendants today) wanted to have every possible gadget and gimmick. So the 1905 sight has five (5) different aiming points, a rear sight leaf made to account for drift, etc., etc. And the windage marking in artillery mils!! (Yes, I know what those are, but I can't tell you everything! Look it up.)
All in all a horrible mess, and totally useless on a real battlefield, as the AEF soon found out. But not surprising that a Model 1901 sight would have been liked by a target shooter.
Jim