Third model of Colt. Some have 5B5 stamped on the chassis, some do not. This was the last model of Colt to have the code stamped on the chassis though. One sighted example just has B5 stamped on it.
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: