From the Wikipedia page 
The Shawnee Runestone is a runestone claimed to have been found in Shawnee, Oklahoma, in the United States, one mile from the North Canadian River, which is a tributary of the Arkansas River.
A photo of the Shawnee RunestoneIt was supposedly found in August 1969 by Jim Estep, a young man of Shawnee as he was taking his 7-year-old brother-in-law, Mikel Lindsay, and another small boy, David Sersen, on a snake hunt. They were walking in the northeastern part of the city along a wooded path that followed a small creek, a tributary of the North Canadian River. There are very few stones exposed in this area and no ledges or outcrops. However, they did find an oval stone about 14 inches long in the weeds, buried about an inch in the soil. When they turned it over, instead of finding the hoped-for snake, they saw a neatly cut inscription of five strange letters on the underside of the stone. The find was reported to Estep's mother-in-law, Vondell Lindsay, who asked him to retrieve the stone. The letters were filled with dried mud. Unfortunately, young Mikel used a frog-gig to clean some of it out.
From the current Wikipedia page on Oklahoma runestones 
Professor Don G Wyckoff. an archaeologist at the University of Oklahoma, examined the Shawnee stone and noted that it is a soft red Permian sandstone, writing that "the inscription is... remarkably fresh and certainly not as worn or weathered as the stone's natural surface. The Survey staff has viewed other exposures of this Permian sandstone which have carved dates as late as 1957 that are more worn and weathered..." Both the Shawnee and Pawnee runestones are products of the modern period. The inscription reads either mldok or midok in standard Elder Futhark lettering.