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.
Intermediate Frequency: 455kc/s
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.