The 9 is the biggest indicator for me. Sometimes it is hard for me to tell the levelness of the numbers.
The small date's 9 will have a tighter curl that points towards the bottom of the 7 whereas the large date 9 points towards the top of the S, like yours.
Ah, the 7 is also a great indicator. I did not notice that one. Edit: Upon further examination, It seems like the 7 pointing to the top of the S may be a bit inconsistent though due to the varied positioning of the mint mark.