Sorry for the full shot garbage. Someone took my camera off my desk used for full shots and not one single nerd in this place will fess up. Could this be the 79D RPM? It looks like its in the right spot and the inside shape of the "D" looks close with maybe some different wear? Possible???? the die scratches are very worn but seem to be there.
@MatrixMP-9 I'm not seeing the shift towards the east on your blow up. Appears to me more likely a die chip.