Hand-made, die struck counterfeit Walking Liberty half dollars are super rare, and that this piece is a key-date is even cooler.  These varieties were struck on sterling silver planchets.  So far, only five different WLH counterfeit varieties have been documented.  This variety was made very well.  A pick-up-point for this variety is the reverse position of the cactus(?) leaf relative to the position of the B in PLURIBUS; on the counterfeit the leaf touches the center of the B, while on the genuine it is to the right-edge of the B.  Other lettering and details are also not exactly the same as the genuine.  The reverse of this die was also used on a 1917 counterfeit WLH variety too, thus making this a small family of counterfeit WLHs.
 
On average, an example of this variety comes up for sale once every year or two making it quite difficult to find if you are looking for a type-coin for your set.