I got a reply from the Ohio DNR today:
Dear Mr. Judy,
Thank you for writing us with your question on turtle shells, antlers, and bone in the making of pens. Snapping turtles can be harvested legally as you may know, with a fishing license. They then can be sold for consumption as food, only. If the shells or other parts want to be sold, they need to be raised and possessed under a wild animal propagation license for commercial purposes. You could obtain the shells so long as you also obtain such a license and keep records of the sale. If your friend just wants to use some of his turtle shells that he legally acquired for you to make him a pen, that would be fine, but it could not be sold.
Antlers that are legally found shed deer antlers can be taken, possessed, bought or sold. Other deer parts such as hides, feet, and also including antlers that were not shed but legally acquired can be bought or sold so long as a statement is kept that lists the previous owners name, address, where and when taken and the number bought and sold. This documentation must be kept with the parts until they are made into a final product, like a pen. The regulations do not list bones, so their sale would be prohibited.
If you have further question on this information or the license information mentioned you may wish to contact the Law Enforcement Section in the Wildlife District Office near you or your local State Wildlife Officer. Their phone numbers are listed on our website on in the hunting and fishing regulations books. I hope this information is helpful and thank you for writing to us.
Pretty interesting stuff.