Second model of Colt, and early versions were not all that different to the original version.
Early 5B4 models used the original ETA round IF cans, later models had newer square IF's
Early versions also used either the ECH41 or ECH42 mixer / oscillator valve (far left hand side looking from the back). This is easily distinguishable from later models which used the improved ECH81 which had no rimlock base like all the other valves in this set.
Bell Colts ran from 1951 through until 1980 - the longest running model of NZ built domestic radio. It saw many different engineering changes over the years, and the last few models dropped valves in favour of new transistor technology. There is considerable information on the main Colt page about this Kiwi icon.
The radios in this series are:
Intermediate Frequency: 462kc/s
Frequency Bands: 1
Chassis Notes(most schematics can be clicked to download a full size version) Early versions used all rimlock valves, however later versions replaced the ECH41/42 with a noval ECH81. Some chassis' were stamped with 5B4, but not all of them.