Washington Quarters Key & Semi-Key Dates?

The 32D and 32S are the keys and the semi-keys to the series would include 34-D, 35-D, 36-D and to a lesser extent the 37-S, 38-S and 39-S (the semi-keys separate from the pack in grades of XF/AU). There are plenty of varieties that add to the key list (34 DDO, 37 DDO, 42-D DDO, 42-D DDR, 43 DD, 43-S DDO, 50 D/S mintmark, 50 S/D mintmark, and to a lesser extent the 34 light and heavy motto varieties, and the 34-D heavy motto).