How to delete plenty of duplicate block instances in the same position?

for special need,I have to uee blocks in my projects.Rhino doesn’t have the command for selecting duplicate blcoks ,only has the “_SelDup“,which is not workable for blcok instance object.Can someone give me some advices for this problems?

Hi Lin -

The SelDup command also selects block instances that are in the exact same position.
Please post a 3dm file when you are running into a case where that is not so.
Also, please run the Rhino SystemInfo command and copy-paste its output here.
-wim