The description of Full Head on Standing Liberty Quarter is misleading many times.  While technically correct perhaps, there can be a full head (or almost as illustrated in the coin here) but the coin could missing other important criteria needed for a top line coin. 

Specifically, also look for the edge of the drapery to be "proud" (raised up) on Liberty's right thigh (missing here) as well as the detail on the shield, the hardest to find complete.  Look for all of the stars around the edge (missing here or at least very week at 7:00 o'clock) as well as nice full vertical lines in the small heraldic shield in the center of the shield on Liberty's left arm (again missing in this one). 

Here's another.   Full Head just barely meets the criteria for that description (in my opinion), but also check out the gouge in Liberty's breast, the questionable complete rim of the drapery over her right thigh, and the very weak inescutcheon.

Another key element is at the opposite end of the coin.  Look at Liberty's toes, particularly on the 1917 Type I issues.  On top flight coins, they should stand out not be mushy or not there at all.