Traditional whet stone horns are still available from Austria actually. To prepare an edge, scythe blades were hammered thin on tiny anvil heads stuck into a log or the ground, stoned , and then hung out overnight to rust the edge and give it bite. During field use they were honed with the stone till they needed anvil peening again. The little anvil/hammer sets are hardly ever seen around here any more, the stones either, but quite a few old horns seem to turn up. I suppose files just took over for crude sharpening as scythes and reaping hooks became ditch wacking tools or even just quaint old decorations rather than integral parts of the harvest and their proper use and the old world sharpening techniques developed to maintain them became another lost art.
Sorry to ramble.
Tim A.