The Columbus model 4 was manufactured for Columbus Radio Centre Ltd by Radio Corporation of New Zealand Ltd in 1952.

A 4-valve broadcast band alarm-clock radio.

Valves (4): 6SA7, 6AR7GT, KT61, 6X4

Chassis Notes (most schematics can be clicked to download a full size version): John Stokes wrote a 2-page article in an NZVRS magazine** on the unusual design of this set and how it appears to have been a grafting of two circuits from the Radiotron Designers Handbook, 4th Edition, 1952 to produce a reflexed superhet.  Its possibly the only commercial use of reflexing in a NZ-built set since the late 1930's when Radio Ltd produced a few el-cheapo 4-valve sets.

** publication date / magazine number unknown at this time

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.