Content Type of Older Versions of the Documents

Hi,

Trying to find the Content Type of a Older version of a document using powershell.

We are trying to delete a Content Type from SharePoint Library from the UI and keep getting the error "Content Type Is Still In Use", have gone through many posts and checked everything like, Checked Out Items, Recycle Bins (User, Site Collection,...), the only thing we couldn't verify is if this content type is used by older versions of the documents as this library has versioning enabled. (#2, from http://hristopavlov.wordpress.com/2008/06/24/content-type-is-still-in-use/).