Manufactured by Bell Radio-Television Corp. in 1951, production ran until 1980.

The Bell Colt was the biggest-selling, longest-running and arguably the best known model of valve radio ever designed and built in New Zealand. The ubiquitous Colt spanned almost 30 years and saw several different chassis versions with 3, 4 and 5 valves, and two different versions of a transistorised model for the last few years of production.

Along with different circuitry, there were many different dial layouts, at least 7 cabinet colours (with various tones of colours as well) and even some different cabinet styles including a light- and a dark-toned solid oak cabinet being offered.
The plastic cabinet dies came from Australia where they were used for the Airzone Cub, just as the previous Bell mantle, the 5E, had used the fragile Airzone 458 cabinet.
You can see the mold marks for the Airzone logo mounting area on the early cabinets, but the dies must have been modified at some stage because these marks are not visible on later models

There are also two different control versions - one has recessed shafts with push-on plastic knobs, and these can be an absolute nightmare to remove if there is any hint of corrosion on the shaft (sometimes needing to be broken off). The other has shafts that pass through the cabinet and these models generally use a grub-screw mounted molded knob more reminiscent of the early-style bakelite knobs. Its common for these knobs to crack, most likely due to overtightening as they have no metallic sleeve.
These are not the only knobs fitted to Colts, and while many arguments arise as to what knobs a Colt SHOULD have, so many of these were produced over the years (more than 6500 in 1961 alone, that's around 20,000 knobs not counting the world-wave models which needed one extra!) that it seems reasonable that the factory would use whatever it had (or could get) if-and-when it ran out of one type.

EXPLORER: A dual-wave model with a shortwave band.
CHAMP: A three-valve set.
PLANET: The oak-cabinet models
SOLID STATE COLT: The Solid State (Transistorised) model from 1973 onward

The Bell Colt was also produced as a Skymaster model for Bond and Bond, and a 'marine' version of the dual wave chassis without tone control was seen in a Fountain model. In 1962 when Bell dropped the Colt in favour of its new 'General Radio' line, Tee Vee Radio Ltd took over production as the 'Tee-Rad Colt' for a couple of years, however they were not successful and production went back to Bell.

Valve Lineup: Various
5B4: ECH41 or ECH42 or ECH81, EF41, EBC41, EL41, EZ40
5B60: ECH81, EF89, EBC81, EL84, EZ80
5B61: Same as 5B60, although later variants had a solid state rectifier
5B67: ECH81, EF89, EBC81, EL84, BY179 Silicon Rectifier

Note: the chassis numbers hint at the model year: 5B4=1954, 5B60=1960 etc - however these chassis codes are not found on the chassis so some detective work is required to find the model you're working with.

I.F. Frequency: Various
5B4: 462kc/s
5B60: 455kc/s
5B61: 455kc/s
5B67: 455kc/s