With the 48-52 serial numbers using letters in sequence, it would make sense to predate the list by backing up the alphabet, that would make yours an early 48 maybe. But no one has compiled a working list, and there are a lot of schwinn nuts out there, so maybe the sequence isn't that easy. I just remembered one more way of checking, and that's the cranks. In the middle portion, there may be a 2 digit date stamp, many Schwinns have it, it's the last 2 digits of the year. But you have to take them out to see that. If you're going to redo the bearings, probably just a cleaning and grease on that women's bike, you can check the year. Also, is there a name on the chainguard?