You can see the history of a post by following the link:

    https://stackoverflow.com/posts/[PostId]/revisions

This will be available via the time on the last edited flair:

![Where to get the revisions][1]


  [1]: https://i.sstatic.net/Bx3aN.png

If there's no last editor you can type the URL yourself, or there is a [StackApp](https://stackapps.com/questions/2138/se-modifications-username-autocomplete-in-comments-inline-revision-source-a) which will add a "history" link to all posts.