Well not only did I finally find a RPM, but it has turned out to be an AU58! Just received it back yesterday from grading service. Very happy with the result. 1938-D/D Buffalo Nickel, 7,020,000 total minted. Designed by James Earle Fraser. RPM appears to be a FS-1938D-501 (Talbert), (Complete Guide to Buffalo Nickels by David W. Lange, page 177) Could there be an "S" under there? It's hard to tell.