Cleaning out the asset library

We had a third party firm work on our website.  Sadly, they did not pay attention to our style guide, meta description length fields, alt-text, you name it.  I'm still cleaning up.

There are several images in the Asset Library that seem to be duplicates of each other.  It seems if one image did not work, they modified it multiple times, and saved each modification, so which one is in use and which ones can be deleted?

I am hoping to find a way that Squarespace could automatically identify and delete the unused images, so we do not have to this task manually. 

Any suggestions?