Purging old version of a design

Hello,

I'm trying to purge old version of a design and although this version does not have any where used object I'm getting message that it is attached : "This version cannot be purged because it is attached to one or more objects. "

How can I verify what is attached to this version?

In the files tab I have a file but the remove button is gray. other then that the where used tab is empty.

Many thanks,

Alon