The Columbus Somerset. This is a 6-valve + magic eye broadcast band radio, and it is believed to be the base model of the 708 Somerset De Luxe, referred to in advertising with short wave. This is all based on advertising pictures and descriptions - actual pictures of a 708 would help clarifiy this.
Intermediate Frequency: 455kc/s
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.