I had a conversation with a relative of an owner of S&R Chevrolet. It was a family owned business that was sold in 1980 as the original owners passed on. I now have confidence that the dealership info provided by NCRS is accurate. My concern had been that I could only find S&R Chevrolet ads up to 1966 in a Mason City newspaper. Many thanks to the secretary of the C.L.A.S.S. Car Club in Clear Lake, Iowa for his help.