The Courtenay 5M was manufactured for Turnbull & Jones Ltd by Radio Corporation of New Zealand Ltd in about 1951.
This model is part of the RCNZ Model 5 series of radios.

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.

Valves (5): 6BE6, 6BA6, 6AV6, 6AQ5, 6X4

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.