It is a type two quarter 1917-1924. It is also a P-mint. Beyond that, I know of no conclusive way to narrow it down any more than that. You did ask for a guess as to what year. I will guess 1923. I have seen a decent amount of SLQs and that year just jumps out at me. It's something about the wear pattern and level of toning. This is of course still basically a blind guess.
It's worth keeping. It's value is probably just the spot value of silver plus a tiny bit, but it's still an interesting coin. SLQs also only rarely come up in junk silver lots so most people wouldn't acquire any unless they specifically tried to.