The Courier QR3 was manufactured by Radio (1936) Ltd in 1929.
3-valve multi-band battery set with "Quenched Radiation".
Incorporating a feature seemingly unique to Couriers at this time, band changes being made with the flick of a switch - most sets in the 20's required coil sets to be changed (the coils were typically wound on plug-in formers).
This set was marketed as NOT radiating any squeals or other interference which some poorly designed radios of the time were prone to do (getting the owners in trouble with the authorities) - hence the 'Quenched Radiation' part of the name
Valves (3): One detector and two audio valves
Frequency Bands: 2
General Construction Notes for Radio (1936) Ltd: Early Radio Ltd. schematics did not show the models, just the year, valves and bands, so some sleuthing is required to find the right one.
Early 30's Ultimate models with three digit model numbers indicated both the number of valves in the set, and the price it retailed for - for example, the model 856 was an 8-valve radio which retailed for $56 pounds. The equivalent Courier models were reversed, so an Ultimate 856 was a Courier 568 (theoretically, at least). This was the Auckland price though, and often the sets would retail for 1 or 2 pounds more in other centres, presumably to cover the freight cost of moving them around the country from the Auckland factory.
Note the use of old resistance terminology on older schematics: ω means ohms and Ω means megohms.
Some 1936-onward 3-letter chassis codes vary the last letter between brands, for example:
BBU - Ultimate model BB
BBR - Rolls (and Golden Knight) model BB
BBC - Courier model BB
All use the same chassis.
Golden Knight, Courier and Rolls appear to use the same copper-painted chassis while Ultimate chassis' are painted silver
After the war a new model code system was introduced, whereby radio models all began with R - the first model being the RA, a dual-wave 5-valve set commonly released in a pressed tin cabinet.