How to tell if iPhoto Library is old (not used anymore)

[musukosan]

When I first got my iMac and used iPhoto and went ahead and imported all my photos into the library. Later, I learned that I could use referenced library. That was about two years ago. Today I noticed that there is a library in my pictures folder named iPhoto Library. Since I named my referenced Library something else, I'm pretty sure the iPhoto Library is the first lib I created and I can now delete it. It's like 95 gigs, so I would like to free up the space. Before I do this, I would REALLY like to make sure this is the first library that I don't need anymore. Any way to tell this for sure? According to Finder, it was "Created" two years ago, but opened recently. However, my referenced library (which is the one loaded by default) has the same "Last Opened" and "Modified" date as iPhoto Library so it has made me second guess my gut. Thanks in advance.