What do you make of this Washington MM?

DHeath

Today I stumbled onto a 68 proof set with an unusual quarter. The area around the mintmark suggests an RPM, and the quarter has pretty obvious MDD. Just wondering if one of you with the quarter book would mind a quick look?

cladking

There really isn't a quarter book. Fiegenbaum mostly just stops at 1964. The Cherrypickers
Guide doesn't list it, and Wexler/Flynn only covers the double dies. There is a DDO for this coin
but this one doesn't appear to be it. I have seen this before but can't really make heads or
tails of it and haven't pursued it. You might consider contacting one of the experts directly.
JT Stanton intends to be doing a work on some of the major varieties, perhaps he'll be familiar
with it.

DHeath

Thanks CK. It isn't a doubled-die. The machine doubling is just interesting on a proof, but Coneca lists three different 68-S proof RPM's and I was hoping Dr.Wiles book might have illustrations. It appears to be south orientation, and there is a large polished area around the new mintmark. Probably not rare or valuable, but pretty interesting.