The model 5M was an updated version of the model 5, using all miniature valves. The tuning arrangement was also modified to give a better spread of the cluttered upper frequencies.The Courtenay 5M is part of the RCNZ Model 5 series of radios.
The first model 5's appeared in 1949 (although the model is widely accepted as being released for the 1950 range), and lasted for around 4-5 years with various changes along the way. The first model used a mix of miniature and octal valves, but subsequent models used all miniatures. Externally they all looked much the same aside from the model 5B which had a slightly wider dial scale, and a slightly narrower speaker grill to maintain the correct width for the model 5's cabinet.
By the mid-50's Radio Corporation of NZ was producing new plastic-cabinet radios like the 504 and 565, and this new versatile and colourful material was rapidly replacing timber as the cabinet style of choice - the model 5 being one of the last wooden mantle radios from Radio Corp NZ.
The radios in this series are:
1949 Courtenay model 5 Talisman
1949 Columbus model 5 Bristol
circa 1951 Courtenay 5M Talisman
circa 1951 Columbus 5M Bristol
1951 Columbus 5A Bristol
circa 1953 Columbus 5B Bristol
circa 1954 Courtenay 5B Talisman
Intermediate Frequency: 455kc/s
Frequency Bands: 1
Chassis Notes(most schematics can be clicked to download a full size version) 5M used all miniature valves as opposed to a mix of miniature and GT valves used by the original model 5. Also had a revised tuning arrangement which spread the broadcast band more linearly over the tuning range. Used a RCNZ 5" EM speaker. The dials are plastic and prone to fogging and cracking from UV damage.
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).