There are other definitions of the word iconic, but the one that sustains the very valid point that Mr. Albert Brecken has made follows below:
An iconic design is usually a design that is ‘ground breaking’ and one that sets new standards in its field. It is a design that other designers and manufacturers follow, as it becomes a bench mark for other similar products. Furthermore, an iconic design is one that stands up to the test of time, remaining a good design, despite the passing of years, decades and even centuries.
Mr. Brecken, I agree with your proposed EP-1 as the iconic locomotive of the NHRR.