The Columbus model 56 was manufactured for Columbus Radio Centre Ltd by Radio Corporation of New Zealand Ltd in about 1941.

5-valve dual-wave with bandspread short wave band. 

Appears to have been a 5-valve version of the venerable model 66 although not nearly as popular given the few examples found today. 

Noted as being similar to model 52S

Valves (5):
56: X65, KTW61, DH63, KT61, U50
56A: 6K8GT, 6K7G, 6B8G, 6F6G, 5Y3
56B: 6K8G, 6K7G, 6B7, 6F6G, 5Y3G

Intermediate Frequency: 455kc/s

Frequency Bands: 2

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

56 service info unavailable, but it has been noted as being very similar to the 52S - see this service documentation and notes for more info:

Service information (RCNZ_-_model_52S_and_56_-_5V_DW_AC_Expanded_Shortwave_Tuning_-_1940.pdf) here

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.