You have an 1899 made in 1899.
That should put your serial number under, IIRC, 11,000.
Depending on condition and specific attributes, you do realize that that rifle could be worth middle to middle high four figures, don't you?
Drilling and tapping such a rifle would legitimately reduce its value by more than half.
If you can't stand the sights, retire it and get another Model 99 of a newer vintage.
"The gift which I am sending you is called a dog, and is in fact the most precious and valuable possession of mankind" -Theodorus Gaza
Baby Jesus cries when the fat redneck doesn't have military-grade firepower.