The original image + versions should be in stacks. First, with all the stacks opened (option+') select all the images, then split the stacks (shift
commandk). As when you create versions Aperture adds "version 2", 3, and so on you can seach by "version" and only the versions will be shown. However the image date will be the master file date so you can't actually make a selection by the date they were modified.
If you add a keyword or 5 star rating to the versions you wanna keep this could be done a lot easier.