Robert_Charlton - 12:32 am on Jul 10, 2012 (gmt 0)
I assume you identified these via eval.google.com. What did they appear to be checking on your site?
Your question is extremely general, so here are some general references. First, a couple of prominent discussions we've had on WebmasterWorld....
eval.google.com - Google's Secret Evaluation Lab
"Rater Hub Google" Rumours?
Google's Human Evaluators - 10,000 of them?
And a recent video from Matt Cutts, which should help to dispel a lot of the common mythology about how directly these reviewers influence rankings....
How does Google use human raters in web search?
Matt Cutts - YouTube - May 1, 2012