Yes it is lettered for Surprise Valley and yes this is the former SVRy 15. Sexton the manager of Eureka Nevada had a scheme to build a Surprise Valley Railroad. He promoted it and said that he had the locomotive and cars to equip the line. He merely remarked some of his EN equipment. He never was able to drum up the backers to actually build the railroad. I think there is a bit about this in Myrick's Railroads of Nevada books. Also Greg Maxwell who posts here from time to time told me last weekend at Sumpter Valley safety weekend that his new book on the E&P/EN is due out soon, so that is something to look forward to!