www.itn.com will show you available fare classes for specific flights. It will not show you this info by default -- you have to create an account, and in your new account's profile, set the mode to "Expert".

The data that ITN shows you for each class maxes out at 9. So if they are 9 or 10 or 11 or 50 seats available, it will still say 9.

What is/was "ticket window"?