Could anyone tell from the show that Ken Osmond was actually two years older than Tony Dow in real life? I found that interesting since I thought that Wally looked older and seemed more mature.

No. To me, they seemed to be about the same age.

Frank Bank looked the oldest.

I think the order is Frank Bank being the oldest, then Ken Osmond, and then Tony Dow being the youngest out of the three. To me, Ken pretty much looked older than Tony, maybe not just in appearance but in acting style, although Tony was taller for awhile. Once they got into their later teens, all three looked about the same age.

Speaking of Ken, I found this website and picture about his son, Christian (who played Eddie Haskell's youngest son, Bomber, on the New LITB)...seems like he's doing pretty well as a veterinarian!
http://www.vshsd.com/images/osmond.JPG
http://www.vshsd.com/doctors/drosmond.html

[QUOTE=HaskellGirl]I think the order is Frank Bank being the oldest, then Ken Osmond, and then Tony Dow being the youngest out of the three. To me, Ken pretty much looked older than Tony, maybe not just in appearance but in acting style, although Tony was taller for awhile. Once they got into their later teens, all three looked about the same age.
QUOTE]

You do have a point. In the later seasons, Ken appeared older because he had that deep voice. So whenever Eddie was kissing up to adults and not acting like his usual self, he seemed more mature.