what does the DDM-FS, and the OMM-FS stand for on some graded older Washington quarters? That FS can't be for Full Step, and why does the FS part have a set of numbers after it to?
FS-Fivaz-Stanton Number catalogue system for die varieties, OMM-Over Mint Mark(eg. 1951 D over S mintmark), cant think what DDM means.
