This interesting sigh dates from the 1910 era . It was used on a tower line that supplied power to a large electrified railway system in western New York . The towers had rather humdrum dark brown four part Thomas multiparts on them . The signs identified the voltage of the line( 66kV) and were numbed for each unique tower .They also have the name Of the New York State Railway co a large holding co that controlled many interurban rail lines in western new york .The line is long gone and the sign was found near the rotten foundation of a long gone line tower. I will try to identify the insulators themselves in a future post.