Native American Peace Pipe

hi all...i was given a Native American peace pipe head from my mother....it was a piece that she received from my Great Grandfathers estate....on the bottom there are 2 letters scratched into the pipe...they were there in the early 1900s when he acquired it.. i guess i was just hoping someone might know a little about these things, and might be able to provide me with any information. i believe it was obtained in the Dakota's....so maybe its Sioux. 

http://i163.photobucket.com/albums/t285/nabes1/PICT0821.jpg

http://i163.photobucket.com/albums/t285/nabes1/PICT0817.jpg