the rear grills look quite different..
the C420 has a smooth "century style" air intake at the rear of the longhood, same style as the other centuries.
the RS11 has an intake that takes up more of the carbody, and grills that stick out from the carbody side, not smooth..
the century has a nice, neat smooth long hood side..no bulging grills like the RS11.
the RS11 also has the round fan on the rear of the roof..again similar to the older RS3 style..the Century has no round fan on the roof.
The nose notches are also different..
the RS11 has "RS11 style notches" and the Cenury has "Century style notches"!
The RS11 notches are much "deeper" than the Century notches.
the RS11 often (but not always) has sand plugs on the notches, the Century does not.
after awhile you will be able to easily tell a RS11 from a high-hood C420 at a glance. they each have a distincive "overall look" that is easy to spot once you are familiar with them..
much like telling the difference between a 1965 and 1966 Ford Mustang..
the differences are clear and obvious once you know what they are..
the C420 is also a much more massive-looking engine than the RS11..
it just "looks" like a Century..while the RS11 looks like...a RS11!
http://220.127.116.11/images/l/LVRS117642 ... .82882.jpg
http://www.trainsarefun.com/lirr/lirr%2 ... 20Park.jpg