Shelby, it is carved into the wood butt plug. On second glance now, it may be the initials 'E D' which have been bisected by the long line down the middle. However, the middle cross stroke on the 'E' does not seen to have the terminal arm that the outer strokes have. The long 'center line' may just be an accidental addition. Would like to have it in hand and take a good close look. For now it is just speculation. Neat horn and appears to be quite old.
Dick