The Columbus model 91 was manufactured for Columbus Radio Centre Ltd by Radio Corporation of New Zealand Ltd in 1950.

Third of the 'Big Bandspread' models (the Model 75 was the first in 1940, the model 90 was the next, in 1948 and this models big improvement was push-pull output, perfect for high output.  Some of the console-model 91's came with a big Goodmans 12" speaker, but most had an EM 10" speaker (91P had a permanent magnet 10" version).

1950 Columbus model 91

Valves (7 + magic eye): 6SK7, ECH35, 6B8, 6SL7, 6V6, 6V6, 5Y3 and 6U5 Magic Eye

Intermediate Frequency: 455kc/s (to be confirmed)

Frequency Bands: 5

Chassis Notes(most schematics can be clicked to download a full size version)

Notes on service material suggest HT is too high and to insert a 250Ω 10W wirewound just prior to the reservoir cap / field coil junction to drop the 300V to around 260V.  Also use 5V4 as 5Y3 is possibly stretched in this role.  Other notes on the schematics in the service PDF - some are difficult to read.

Service information (RCNZ_-_model_91_-_7V_PP_AC_-_1950.pdf) here

1950 Columbus model 91

1950 Columbus model 91

1950 Columbus model 91

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.

All documented models using this chassis (2 in total)

1950Columbus model 91 - this set
1950Courtenay model 91