Found this in a collection of coins I bought from a friend. I was going to sell it along with several other duplicate coins that I already had in my collection until I noticed the mintmark looked funny. Closer inspection revealed what I am pretty sure is hub-doubling and not machine doubling on the lettering on the reverse. It looks like FS-25-1964D-801 aka Coneca DDR-001 according to my copy of the Cherrypicker's Guide.
Not seeing the notching characteristics for the FS-801 and the E of EPU diagnostic is not present. MD...because... ...the mint mark was added to the working dies after they were created with the working hub. Both the design and the mint mark would not each have doubling, but the working die could have resulted in a RPM. What is visible and apparent is MD...imo...Spark