These are apparently quite rare. Here's a sign on the Muskogee Turnpike:
(https://www.aaroads.com/forum/proxy.php?request=http%3A%2F%2Ffarm5.static.flickr.com%2F4012%2F4686636171_8fd4a01891.jpg&hash=db82e1c56b5d4c1a7276ff52d4e7a1916a1e3272)
If you have any similar pictures, post them here.
(https://www.aaroads.com/forum/proxy.php?request=http%3A%2F%2Fwww.denexa.com%2Froadgeek%2Froad-photos%2Fmain.php%3Fcmd%3Dimage%26amp%3Bvar1%3Dtpks%252Fchickasaw_tpk%252FIMG_0977.JPG%26amp%3Bvar2%3D700_85&hash=f46fb3f701dceddc2f7eb448af29632bfba851bd)
The Chickasaw Turnpike crosses exactly one county line, and it is signed.