“Tack indicates location of poster.”
We found this survey marker by the Tar Kiln Trail in Piney Creek Wilderness. It’s quite hard to see, but I was able to make out that the tack in the center marks the place where this post is on a grid.
I believe this is a reference marker, or “bearing tree”. It means that it points to where the actual survey marker is (or would be if practical). This sign indicates that the marker is 8 chains* away, bearing west. As that direction was a very steep slope, I suspect this reference is all there is to indicate the marker designating the land corner. The 36 squares you see on this sign are the 36 square miles in a township.
Latitude: 36° 40.727’N
Longitude: 93° 35.686’W