Radio Corporation of New Zealand started as a part-time business in Wellington and grew to one of the largest electronics firms in the country. In 1930 William Markoff started making amplifiers and winding transformers in a small shop in Cornhill St, and the company was formalised in 1931 as W. Marks Ltd (Markoff having changed his name to Marks after settling in NZ from Russia after WW1).
Also in 1931 Marks began manufacturing radios, and struck a relationship with Stewart Hardware on Courtenay Place who became the distributors.
By the end of 1932 Marks had changed the company name to Radio Corporation (N.Z.) Ltd, was employing nearly 50 staff and was producing 500 radios per month.
In 1933 RCNZ moved to new larger premises in Courtenay Place, having outgrown the original premises. Around this time Stewart Hardware went out of business, and a new company, Courtenay Radio Ltd, was formed to continue the distribution of radios. Other 'private' brand sets were also commenced at this time, including Acme, Pacific, Stella and CQ.
In 1934 Turnbull & Jones of Courtenay Place took over the distribution of Courtenay radios, and also had a line of RCNZ coils and transformers (and later radio kitsets) made for them under the brandname Exelrad.
By 1936 the strain of short uneconomical runs for the private brand sets meant the company needed to change. It was reorganised as a public listed company and renamed Radio Corporation of New Zealand Ltd. All agreements with private brands other than Courtenay were terminated shortly after and a new house brand, Columbus, was introduced. The last private brand sets were produced in 1937.
in 1937 RCNZ set up a subsidiary company to run a nationwide chain of stores, Columbus Radio Centres, for the distribution and servicing of Columbus radios.
It is worth noting that RCNZ manufactured as much as it could - mica and paper capacitors, transformers, speakers, bakelite knobs, valve sockets, wafer switches... and they had the ability to etch and screen print their own dial glass, press and cadmium plate their own chassis' and produce a set that was on par with anything that could be imported from the US.
The war curtailed manufacturing somewhat, and post-war sets started slowly due to shortages of supply, but RCNZ continued on as it had, producing good quality sets.
In 1956 Turnbull & Jones ceased trading in radios and the Courtenay name disappeared from use with the model 45 and 46 (BC and DW respectively) being the last models to be sold under that name.
Around that time Australian Radiola sets began appearing in the Columbus lineup - badge engineering at its finest... but this was the beginning of the end for RCNZ and the Columbus brand. In 1958 Radio Corporation of New Zealand Ltd sold out to Pye and by 1961 the once-massive Columbus name had disappeared from the landscape.