I've been married for 24 years , so as you can imagine I don't do my boning :)
That type of sheath is what's called Wet Molded .
The leather is wet with water and then moulded to shape using what is called a bone folder ( that's maybe where you got the boned thing from )
Here is a work in progress picture , this one isn't Molded as tightly to the contours as the other one , but you get the idea , my bone folder can be seen to the side of the sheath .
http://i943.photobucket.com/albums/a...ps6fafa5e2.jpg
Ken