Ohio State Route 537 is a very short, jagged route in the hills of southwestern Monroe County. The route begins at Ohio Route 260, and it overall trends toward the east. The east end is only a few miles away from the west end, and it lies at Ohio Route 26 south of Graysville. The western end of Ohio Route 537 is very close to the eastern end of Ohio Route 565, so I don't know why these aren't the same route.
My photo for Ohio Route 537 signage shows a northbound junction marker at the western end. The junction marker in the photo helps northbound travelers on Ohio Route 260 anticipate the upcoming turn onto Ohio Route 537. This photo was taken in March 2021, during the grand tour around southeastern Ohio.