Introduction: Need Help Identifying This Bayonet

This item is new to my collection, and I am having a hard time identifying it.  Any thoughts are greatly appreciated.

Overall length is 15"
Blade is 9.75" - 10"

both the weapon and sheath have "61885" stamped on them.  Sheath has an unrecognizable symbol stamped on opposite side of number stamp.

Blade is only sharpened along one edge.