The N.Z. Vintage Radio Project

Rola was probably the single-most common speaker brand used in New Zealand manufactured sets through until the mid-1960s, when Plessey took over the company.  It wasn't a radio manufacturer ^{(see footnote)}, they only made speakers - so while you might only be able to find a Rola label in your radio, it is almost 100% certain that the radio itself is not a Rola.

Rola speakers were initially imported from the US, UK or Australia, then later manufactured or distributed under license by Swan Electric Ltd in Wellington.  Eventually a dedicated Rola New Zealand factory (Loudspeaker (NZ) Ltd) was set up to fulfill the local requirements.  Then, some time in the 60's Plessey purchased Rola, taking over the Rola name.

Rola speakers were imported to New Zealand as early as 1927, with adverts of 'daily demonstrations' of the new Rola cone speaker by Superadio Ltd of Queen St Auckland.  These would have been separate stand-alone speaker cabinets as was the style of the day - radios typically being a small wooden or metal cabinet just containing the electronics.

Rola started in the United States of America in 1924 to manufacture speakers for the new and blossoming radio industry.  In 1930 Rola (Australia) Ltd was formed to assemble and distribute speakers for the Australasian market, and by 1934 Rola speakers were being manufactured in the United Kingdom by British Rola, an offshoot of the parent company.  In the early 1930's speakers used in New Zealand manufactured radios were sourced from all of these locations, and this can cause some confusion as to the country of origin of some NZ-built radios since the speakers are such a prominent item in a radio, and Rola speakers, in particular, had the country of manufacture on the label.

It is also possible to find Rola speakers with the country of origin painted over (note the silver paint at the bottom of the logo) - According to John Stokes' research this was a practice employed by Radio Ltd to support the 'Be British, Buy British' sentiment of the day - and so speakers sourced from the American plant would have their manufacturing location obscured.  JWS refers to this as a deceptive practice, however given that the speaker was such a prominent item in a radio, and that radios did not generally have a back panel, its almost understandable that they did this so as not to confuse potential customers as to the origin of the set.

Dating Rola Speakers:

There is often a code stamped on the rim of NZ-made Rola speakers which allows you to date them, and potentially date the radio (assuming its an original speaker).  It should take the form NLN or NNLN (number letter number or number number letter number).  The first digit or two digits are the day of the month, the letter is the month (A = Jan, B = Feb etc) and the last digit is the year - just leaving you to figure out the decade (electromagnetic speakers are probably 1930's and early 40's, PM speakers are generally post-WW2 - boyoind that it takes a little sleuthing).

Some Rola speakers are more commonly seen than others - for example the K8 EM speaker found in many early radios and the 5C, a 5-inch general-purpose speaker that was produced in vast quantities and was found in many 1950's-60's bookshelf and mantle sets.  The 5C was characterised by its black dome-shaped magnet housing often with output transformer bracket pressed over.  a common transformer used with this was an LCG72 where the set used an EL82 output valve (such as the Bell Colts between the mid 1950's and into the 60's).

Footnote: There were a few (very rare) Rola branded radios sold around 1930 - but this is unlikely to have been the Rola Speaker company making these.

 

References:

The Golden Age of Radio - John W. Stokes (out of print)

Graces Guide to British Industrial History - https://www.gracesguide.co.uk/British_Rola

Harvard University - http://waywiser.fas.harvard.edu/people/8658/rola-company