I installed this in version 0.7.57 using the newest version of plugin updater and get this error when I try to open the drop down menu. I get a different version of this error when I just click the Find Duplicates icon on the toolbar.
Traceback (most recent call last):
File "calibre_plugins.find_duplicates.action", line 113, in about_to_show_menu
File "calibre_plugins.find_duplicates.action", line 131, in update_actions_enabled
AttributeError: 'FindDuplicatesAction' object has no attribute 'duplicate_finder'
I had version .3.0 I think and it worked ok.