Quadrafire:
The wing bone call is probably the first turkey call ever made and was probably made by the native Americans to call in turkeys. It is fashioned by joining different sections of hollow wing bones and when used properly produces some of the most realistic yelp's and clucks I have ever heard. The problem is that they are very hard to master. The popularity of slate, glass friction calls and wooden box calls have all but made the wing bone call obsolete. There is one manufacture-of a variation of the wing bone call called a tom turpin yelper. I used one of these for years but again it's hard to master and I have better luck calling birds using friction calls.
I've attached a pic of a typical wing bone call.
Good Luck
Jeff
A.K.A. Kuduman