The lettering (IN GOD WE TRUST) is proportionally larger on the half. On all the images I've just googled, the lower edge of the headband points to the left edge of the U in TRUST on halves; on quarters, it points closer to the right edge of the U.
This is just a guess, but it looks like the stars are closer to IGWT on the 50c than they are on the 25c. Chris
I'm looking at the 3rd star down on the right relative to the tip of the nose. The quarter has the inside point of that 3rd star traced in a straight line would travel below the tip of the nose, whereas on the half, the same line drawn from the same point on the same star would terminate on the nose itself.
I'm not sure what the distinguishing characteristics are, but if you look at enough of them you can tell which is which just by looking at the obverse.
Barbers in mid grades are not easy to buy at those prices. Nice good for grade coins will cost more as the demand is there.
The easiest way is look at the R in TRUST. On the quarter the bottom of the R is partially covered by leaves. On the half it isn't.