Early Atlas and Con-Cor, without their contributions in the late 60s and early 70s, I don't know that N scale would be as popular as it is today.
Atlas 0-8-0 circa 1972
Con-Cor Y6b circa 1976, though MRC came out with the originals in 1970, only 4 years after the scale was first introduced to the marketplace. Con-Cor bought out the molds and retooled and re-engineered these with the aid of Rivarossi.
All the latest engines are great and run like fine watches but offerings like these kept folks trying out that corn fangled new scale.

Atlas 0-8-0 circa 1972

Con-Cor Y6b circa 1976, though MRC came out with the originals in 1970, only 4 years after the scale was first introduced to the marketplace. Con-Cor bought out the molds and retooled and re-engineered these with the aid of Rivarossi.
All the latest engines are great and run like fine watches but offerings like these kept folks trying out that corn fangled new scale.