I have not seen a lot of info on this instrument that has a great history.
I make mine from Wood, and different ribs (cow, Elk, buffalo) and enjoy them quite a bit. I play both one and two handed.
Wood
Bone

Here's' a shot of a different set in my right hand in playing position. These are pretty thin.
Notice for playing that the middle finger keeps the one bone stationary and the ring finger is lightly touching the moving bone.


Here's some info from World-beats.com.
Second to that of the human voice, "bones" are the oldest Irish percussion instruments and instruments in general, known to man. 2.5 million years ago, bones, stones and wood, then used as tools, were also one of our first forms of musical instruments. Idiophones, like the Irish percussion instruments the bones and spoons, are instruments that produce their sound from the substance of the instrument itself. Similar styles of playing bone, wood and even stone are found all over the world stretching from South India to Mongolia, to the six Celtic regions of Ireland, Scotland, Wales, England, Bretagne, France and Asturias-Spain. To hold and play the Irish percussion instrument, two bones are cradled in one hand and balanced vertically while the forearm and hand produce a rotating and waving motion, allowing the bones to pendulum and strike each other producing sound.