1957-D Washington Quarter PCGS MS66, COLOR

A pretty quarter pulled from a mint set with toning ranging from orange to aqua-green. For the life of me, I don't understand the grade as there is not a single mark on the coin!
Country:  United States 
Denomination:  .25 Dollar 
Date:  1957
Grade:  66 PQ 
Grading Service:  PCGS 5863.66/38214356 
Metal:  Silver 
Fine:  .900 
AMW:  .18084 
Item #:  9609-052-1 

Price: $69.95