All prior moving coil carriage receivers from the NC-100 to the NC-240C followed the same naming format. The C was for Commercial, and a CS model was Commercial Special. There were other variants built for specific customers.
The NC-240D (the D was for Dual Range since it had General Coverage and Bandspread for the 80-10M ham bands followed the same path but due to some error in typesetting it came out as NC 2-40-D in the ads which made no sense. Internal documentation from Engineering to Production to Service Dept used the original format. It was even used in a June 1968 brochure listing the company history and milestones.
My involvement during 1963-69 was in the Service Department as Tech and Manager and in Engineering as Sr Engineering Aide. My NC-240D collection includes a first run 1946 model which shares a lot of the earlier NC-200 features plus a 1949 version.
I use the later version NC-240D often on CW and AM in the vintage radio part of my ham station along with a similar age Johnson Viking I. It is very stable after a short warm up and sensitivity on the higher frequencies far exceeds the competition which I have also restored and compared using restored vintage Hewlett Packard and other high end test equipment as I used at National Radio.
My NC-240D ratings below are based upon what was the norm when it was built.
Es un equipo receptor exelente para quienes gustan de las antiguedades, a pesar de sus años tiene muy buenas prestaciones, es muy buen equipo, , un lindo adorno por la presentacion de su frente con los apliques tallados, la unica falla que le encuentro es en los contactos de las bobinas de sintonia que hay que retocarlas a veces, pero es minimo esto por la antiguedad que tiene.