Ben,The following may give you some help in finding the information you are looking for.
From 1796 to 1802, Muskingum Co., OH was part of an area called the U.S. Military District.Muskingum Co. was formed in 1804 and the first tax records are available for 1810 and 1816.Land grant records for Muskingum Co. begin in 1804 when OH became a State.We can't at this point answer your question from the records we have in our Neff Family Historical Society's database.I think the land and tax records will uncover the connection you are looking for and provide a clue to whose will you should request to confirm your findings.
I would sugest ordering a copy of of Carol Willsey Bell C.G., OHIO GENEALOGIAL GUIDE.Her last known address I have is: Bell Books,4649 Yarmouth Lane, Youngstown, OH44512-1749. I tried to phone her this week but the number had been disconnected.
Found the following at @ Amazon.com. OHIO GENEALOGICAL GUIDE, by Carol Willsey Bell (Paperback - 1987) 2 Used & new from $19.95 Other Editions: Unknown Binding. You will find it a worthwhile investment in helping with your reseach.
Would also suggest posting your query on the Neff message board at Rootsweb.com.We watch that board on a regularbasis.Let me know if we can be of further help.Bill NeffNEFF FAMILY HISTORICAL SOCIETY, Harrisburg, PA