5-valve broadcast band radio, referred to in Columbus literature as the "Radio for the Smaller Home". One of a pair of radios in that category that Radio Corp of NZ released just post-WWII. This is broadcast-band version of the model 55 Corvette.
Original sales booklet for the model 53 and 55 available for download here.
From the sales booklet:
The five-valve radio has held, and will always hold a prominent place in New Zealand homes for the reason that most of our larger centres have excellent coverage from nearby broadcasting stations which cater adequately for the entertainment needs of a large proportion of the listening public.
Therefore, in the knowledge that many people will choose five-valve radio in preference to higher-powered and more expensive models, Columbus has been concerned to provide in its range, two designs capable of superlative reproduction of local programmes but which will, if need be, reach further afield for distant broadcast and shortwave programmes.
In both Model 53 (broadcast only) and Model 55 (dualwave), emphasis is strongly upon quality of tonal reproduction tonal luxury, if you will, at the highest levels that modesty of cost will permit.
To reach this result, modern techniques of tonal control, which hitherto have been reserved for larger and more expensive radio, have been incorporated into these models and this inherent quality of design is further supplemented by the use of an 8-inch high fidelity loudspeaker and the acoustic advantages of substantial cabinet size. It is not usual to-day to find attributes such as these in five-valve radio, but it is precisely from such practice that Columbus is able to derive the undoubted superiority of performance of these models.
Intermediate Frequency: 455kc/s
Frequency Bands: 1
General Construction Notes for Radio Corporation of New Zealand Ltd:
The first digit of the serial number typically indicates the year of manufacture of RCNZ chassis' (although not the decade - that requires a little knowledge of the valves, construction, etc). Sets from around 1934 onwards were often (but not always) constructed in a distinctive pressed 'baking pan' style chassis, seemingly unique to RCNZ.
Model codes beginning with a 0, for example the model 051, are Osram valve versions of the model without the leading 0. Technically the 0 should be an O (for Osram), however the digit 0 was used throughout the site before this fact was discovered.
The E suffix indicates a magic eye option is fitted (in models which were available with or without, such as the model 25).
A and B suffixes appear to be simply updates to the current model, R also appears to be simply an updated model ('R'edesign, perhaps?)
P indicates either a permanent magnet speaker version of a model which also came with an electromagnet speaker (the model 26 for example), or a portable model (like the model 694P).
N and M indicated miniature valve versions of a model which started with all (or a mix, ie: model 5) of larger valves. One of these two codes may indicate a transitional mixture of octal and miniature - clarification is required.
S often indicates a stereo model. It can also indicate 'self-biased' in the transition period between back-biased and self biased sets where there were models with both methods employed (53S for example)
Finally, other suffixes and prefixes make occasional appearances in the RCNZ lineup - like the 66W (a variant of the long-running model 66) and the 75XA (a 10-valve version of the model 75 with a separate amplifier chassis).