Look for a reply from rednichols. He wrote a book that includes the S. D. Myres and his products. Of course, S. D. Myres was originally in Sweetwater, TX 1893-1920, and then moved to El Paso. Pictured here is my currently-owned S. D. Myres holster. Notice that it reads "El Paso, Tex." The maker's stamp variety may determine the age.
See also the Obit that I found on Sam D. Myres in post #3.