Google launched their manual action viewer back in August of 2013. The question was, would Google show manual actions dating back years before that, if the manual action still existed?
The answer is yes.
I asked Google's John Mueller this on Google+. I wrote:
The Google Manual Action viewer launched in August 2013, would it have shown manual actions received prior to the launch (if they still existed), let's say dating back to 2012?
John responded, yes it would. He said:
sure, if there's a manual action, it'll be shown.
So I guess even manual actions dating back to 2010 or so, would be shown, if they still existed.
Forum discussion at Google+.