The curl of the 9 will point down or across. The barb inside the 9, the end will be sharp or blunt. The 7 will be high or low. LIBERTY will be weakly or well struck. Those are the key markers. Examine this photo and compare it to your coin.
Go by the crease in the 7. The small date doesn't have a crease in the 7. The point of the 7. The large date does.