Most Helpful Guy
He thinks you look good and was curious to see what the rest of you looks like. If its suttle its a good compliment. If he locks eyes with you at the end he's inviting you to talk to him. Obviously there's a time, place and way to do this, otherwise it can be creepy.
Most Helpful Girl
I know people, myself included that do this, mainly when they see someone new because they want to see the whole person.
But yeh, generally it means he checking you out.