Two "look at" keys

[Uberbob]

I read on this page that there are apparently two "look at" keys:

Always use both of your "look at" keys on things. Often, they both produce different results.

 

After consulting the game help, I saw that there are in fact three such keys: S, E, numpad 5.

 

So far I've only been using E. I'm guessing that one of the other two is a duplicate, while the remaining is the mysterious second "look at" key, but they all result in the exact same responses from Manny in my game so far. Could someone shed some light on this for me, please?