I have examined this coin, which I probably tucked away in the late 1960s and forgot about it along with the rest of my undated Standing Liberty quarters, and I can't determine if it's a 1916 or 1917. I'm leaning toward 1917, but then I see possibilities, that it could be a 1916.
So worn out- it's hard to tell. Looks like a 1917 to me, though. Also, 1917 had two varieties- Type 1 and Type 2. Yours looks to be Type 1.
1917; were it a 1916, I believe there would be a space between the drapery on the left obverse and the pedestal.
1917 like others said, plus the head does not break into the beading at the top of the obverse and it looks like two hair curls.