"The Diamond Coal Co.'s Mine Evansville, Indiana" The mine, which operated at least as early as 1890 and was on Stringtown Rd., and remained in existence at least as late as 1912. There is no mine at this location today. This postcard is an advertisement for the company, with text on the back claiming this was the "Cleanest Coal in Town. The address for the office was given as 217 Upper 6th St.